Muktol

Personally I'm no big fan of "Foundry Street Denizen" in decks that don't use "Krenko, Mob Boss" or a huge load of summoning spells like "Krenko's Command". He will get +1 or +2 per turn, depending on what you draw, and what you are able to play. The problem is, that he has no evasion or trample, so that even a small x/1 can block him. If you don't play any spells he is a 1/1 without any usefull ability.
I would remove "Akki Avalanchers" for something like "Legion Loyalist", "Mogg War Marshal", "Warren Instigator" or "Quest for the Goblin Lord".

Greetings
Muktol

I would try to reduce the number of different spells and increase the number of the remeining ones, to give the deck some continuity.
I don't mean to offend you, but you could find some tipps in my deckbuilding guide: http://www.mtgvault.com/muktol/decks/how-to-build-a-deck/

Greetings
Muktol

Some suggestions based on my own monoR Goblin deck (http://www.mtgvault.com/muktol/decks/monor-tribal-goblins/)
Remove "Foundry Street Denizen" and add "Quest for the Goblin Lord" ({R}; enchantment; Whenever a Goblin enters the battlefield under your control, you may put a quest counter on Quest for the Goblin Lord. As long as Quest for the Goblin Lord has five or more quest counters on it, creatures you control get +2/+0) instead. It buffs all of your creatures and without spells like "Dragon Fodder", "Kuldotha Rebirth" or "Krenko, Mob Boss" himself, "Foundry Street Denizen" won't get that big. Also he lacks trample, so even a simple 1/1 could block him.
As you are using "Goblin King" you could give "Blood Moon" ({2}{R}; enchantment; Nonbasic lands are Mountains.) a try. This could extremely slow your opponents when they are using many non basic lands.

Greetings
Muktol

If you're using a whole load of swords you should try to reduce the mana-costs of the other artifacts.
I would also increase the number of "Swiftfoot Boots" to 4 and maybe add "Ring of Evos Isle" to give your creatures some protection.
You could also try to reduce the number of lands by 1-3 as your manacosts are rather low, and "Puresteel Paladin" lowers them further. But do some testgames to ensure you get enough mana.

Greetings
Muktol

Keep the Lavamancer, I talked with some friends, who specialice on burn, and they said that the Lavamancer is set in many burn deck.
Personally I simply don't like exiling cards from my grave, and the damage is 'just' a "Shock", but it uses a ressource that otherwise would be left unused ;)
Deppending on your game-surroundings you could use "Blood Moon" in your main deck,

I would be affraid of not drawing a creature with only 12 in the deck. But some testgames/ testdraws should show if that fear is eligible.
You could also try to lower the number or Forest by 1-2, as you have rather low manacosts (My own monoG Infect deck http://www.mtgvault.com/muktol/decks/monog-infect/ plays with 18 lands)

Don't know GyKx's deck but I would use some more creatures. "Blight Mamba" or "Signal Pest" could be used to fill up the ranks.
I'm a fan of "Evolution Charm" as it is really flexible.
Maybe change to some duallands or searchlands to make shure you get the mana you need.

Greetings
Muktol

I would reduce the number of cretaures a little bit (e.g. remove/ sideboard "Grim Lavamancer")
Furthermore I would remove "Char" as it is rather expensive to play and "Pulse of the Forge" because you want to be fast and thus lower your opponents lifepoints faster than he does yours.
An alternative could be "Browbeat" and/ or to increase the number of "Magma Jet" in the deck.

Greetings
Muktol

With all those fog-elements I would use "Isochron Scepter" ({2}; Imprint: When Isochron Scepter comes into play, you may remove an instant card with converted mana cost 2 or less in your hand from the game. {2}, {tap}: You may copy the imprinted instant card and play the copy without paying its mana cost.)

Other cards with might help you would be:
Kami of False Hope ({W}; 1/1; Sacrifice Kami of False Hope: Prevent all combat damage that would be dealt this turn), Primeval Titan ({4}{G}{G}; 6/6; trample; whenever Primeval Titan enters the battlefield or attacks, you may search your library for 2 lands and put them into play tapped)
Ethereal Haze ({W}; Prevent all damage that would be dealt by creatures this turn)
"Hallow" ({W}; Prevent all damage target spell would deal this turn. You gain life equal to the damage prevented this way) could be used in your sideboard.

Greetings
Muktol

Decide if you want to use either "Malakir Bloodwitch", "Mirri the Cursed" or "Drana, Kalastria Bloodchief"" as finisher. If you stay with "Drana, Kalastria Bloodchief"I would reduce the number of by 1-2 (legendary)
Remove "Exsanguinate" and add some more removal spells
"Vampire Hexmage" can be put into the sideboard. I now he is strong, but there are better vampires, e.g. a 4th "Bloodghast" or a 4th "Vampire Nighthawk".
I you have any free slots I would take a look at "Vampire Nocturnus" or "Bloodlord of Vaasgoth"
Perhaps change from "Grasp of Darkness" to "Tragic Slip"
I also would remove "Dreadship Reef" for some more swamps or searchlands. The Reef is very slow, and you don't need blue mana in any of your cards. Also it doesn't count for "Tendrils of Corruption"
As for the sideboard, I personally love "Evil Presence" as it can 'destroy' your opponents mana-base, especially if he uses duallands

Greetings
Muktol

For a token-heavy deck I would remove "Afflicted Deserter" (Sideboard) and "Scorned Villager" (Do some testgames, but I feel that the additional ramp won't be missed). Use the free slots to increase the number of "Mayor of Avabruck" to 4.
With the remaining slots I would either use some more protection, e.g. "Vines of Vastwood", something to push your creatures e.g. "Instigator Gang" or some removals, e.g. "Lightning Bolt" or "Searing Blaze"

Greetings
Muktol

Thanks to Neoxtreem:
-2 "Mountain"
+2 "Nykthos, Shrine to Nyx"
-1 "Furystroke Giant"
+2 Purphoros, God of the Forge

Playing to many high-mana creatures isn't really good, as you want to have them as finishers. Until that, you need something to protect you, and keep your opponent down and that's done with small and flexible creatures.
I think you have a good ratio between cc2 and cc3 creatures.

Looking good so far *like*
But I would reduce the number of "Captivating Vampire" by 1-2 and also reduce the number of lands by 2-3.
The free slots should be filled with either point removal (Lightning Bolt, Terminate, Dreadbore), carddraw (Sign in Blood, Read the Bones) or some more utility (Guul Draz Assassin, Vampire Nocturnus, Curse of Stalked Prey)

Greetings
Muktol

If you have enough removal, the Blade will work very well.
Leaving 2 "Guul Draz Vampire" as finisher is an option you could try
In 90% of the time "Gatekeeper of Malakir" will be played as cc3 rather than as cc2 creature. "Captivating Vampire", but not more than 3 of him.
"Nirkana Cutthroat" is rather expensive to play, cc3 for a 3/2 with nothing and cc6 for a 4/3 with deathtouch

*like*
I would remove "Guul Draz Vampire" for some more "Shadow Alley Denizen" and an additional "Vampire Nocturnus"

Greetings
Muktol

Try to reduce the number of different cards and increase the quantity of the remaining ones. This helps to give a deck continuity and execute the strategy it was built for.

If it was my deck, I would do the following changes:
-1 "Captivating Vampire". Having more than one Captivating Vampire on the battlefield is not necesarry. His second ability can be activated as often as you can pay for it (he doesn't have to tap for it) and his first abiliti is nice, but he is not includs and thus can be remo0ved even with a "Shock"
+1 "Bloodghast". One of the best black vampires there is. Maybe add some sac-lands to your manabase to thin out the number of lands you draw and to activate the effect more often.
-2 "Guul Draz Assassin". You have to invest cc1+cc2+cc2 into him to remove x/2 's which is rather expensife. Often you will get threads which are way bigger tnan x/2 and need to answer this in an instant.
+2 "Gatekeeper of Malakir". Can also remove indestructible and hexproof creatures, depends a little on the deck you're up against. Token and other mass-decks will only laught at him and sac a 1/1, other decks probably not.
-4 "Nirkana Cutthroat". cc3+cc3 for a 4/3 deathtouch is very expensive.
+1 "Kalastria Highborn". One of the best vampire utility creatures
-2 "Blood Tribute". See below
+4 "Doom Blade" or "Go for the Throat" or "Murder". Point removal is always a good thing
-4 "Child of Night". There are better vampires and you need to come down to 60 cards.

"Shadow Alley Denizen" ({B}; 1/1; Whenever another black creature enters the battlefield under your control, target creature gains intimidate until end of turn) could be worth taking a look at.

Blood Tribute: {4}{B}{B}; kicker: {tap} an untapped Vampire you control. Target opponent loses half his or her life, rounded up. If Blood Tribute was kicked, you gain life equal to the life lost this way.
Without acceleration it can't be played earlier than turn 6, thats if you start with 3 lands in your hand and draw 3 additional lands until turn 6. Until that you will allready have attacked your opponent and removed a great deal of his lifepoints, especialy if e.g. "Vampire Nocturnus" comes on turn 4 and activates his ability, or you have a flipped "Bloodline Keeper". Let's say you have your opponent down to 12-14 lifepoints and you play "Blood Tribute": You spent cc6 on a spell that removes 6-7 lifepoints and are not able to play anything else this turn. Even a "Shock" has a better mana/damage ratio. If you want to keep it, sideboard it, and use it against e.g. lifegain decks, or decks which hide behind some defenders you have trouble getting through

I hope I was able to help you a little bit
Greetings
Muktol

Forgot about "Glimpse the Unthinkable" ({U}{B}; Target player puts the top ten cards of his or her library into his or her graveyard)

I would add 4 more creatures. With just 12 creatures there is a chance of having not a single creature on your starting hand.
Remove "Darksteel Plate". Expensive (cc3+cc2) to play and your creature shouldn't need indestructible. Protection like hexproof or shroud (berawe, shroud prevents you from equipping anything more to this creature!)
"Inquisitor's Flail" is questionable. Great in offense and defense for double strikers, but a simple 1/1 creature still will block all of your damage if your attacker don't has trample.
"Loxodon Warhammer" is questionable. Rather expensive to play (cc3+cc3), if you want to get trample, "Horned Helm" could be better here.

For the sideboard:
Dispatch, Leyline of Sanctity, Immortal Servitude, Proclamation of Rebirth

Some suggestions, based on my monoW equipment (pauper) deck (http://www.mtgvault.com/muktol/decks/monow-pauper-equipment-2/) and my monoW Kor equipment (modern) deck (http://www.mtgvault.com/muktol/decks/monow-kor-equipment/)
Etched Champion ({3}; 2/2; Metalcraft -- Etched Champion has protection from all colors as long as you control three or more artifacts), Ornithopter ({0}; 0/2; flying)
Basilisk Collar ({1};{2} to equip; Equipped creature has deathtouch and lifelink), Cranial Plating ({2}; {1} to equip; Equipped creature gets +1/+0 for each artifact you control), Swiftfoot Boots ({2}; {1} to equip; Equipped creature has hexproof and haste), Horned Helm (72}; {1} to equip; Equipped Creature gets +1/+1 and has Trample), Infiltration Lens ({1};{1} to equip; Whenever equipped creature becomes blocked by a creature, you may draw two cards)
Darksteel Citadel (Artifact Land)

I hope I was able to help
Greetings
Muktol