JerichoPumpkin

Bloodflow Connoisseur is my favourite, but you could use also Greater Gargadon or Grimgrin. I think that for modern you got no other "sacrifice only" choices (aside from Nantuko Husk and similar cards)

Legacy Weapon if you want fun. I used it on my good old Elves with priestess of titania and nomad elf :)
Or any other penta color card

as splash of black and Rohgahh of Kher Keep? an also a splash of green to add Prossh, Skyraider of Kher?

not modern: Grollub and Spirit Loop
modern: Congregate, Devour Flesh

another nice taxer is Spelltithe Enforcer, but there's nothing I can find like Rhystic Study

mmmh, nothing comes to mind right away. Ghostly Prison can be an alternative to Sphere of Safety if you want a earlier attack stopper (even if it's less effective late game)

you're right, I should've checked. Tnx, yuo reminded me that Legacy just is not for me. WTF, I understand banning Memory Jar or Demonic Tutor, but Mind Twist?

if you reduce Sol Ring to a single copy, it should be legal in Vintage and Legacy

I would swap out Quilled for Sidewinder, since flanking, like exalted, activates for each occurence on the card

It may seem trivial, but what about Phyrexian Dreadnought? With Dark Ritual and Torpor Orb you could get a really nasty first turn

Well, I guessed that "obscure" was intended for the other users, not for you.
Praetor has always been a favourite of mine, but I never managed to get my hands on a copy. I really miss the good old days of Fallen Empires...
And remember. no Breeding Pit, it's a challenge after all ;)

On a side note, I was totally oblivious of how cool Soul Exchange is nowadays.

What about Ebon Praetor? With all those Thrulls in Ravnica, I'm sure you can manage without a Breeding Pit

EDIT: I forgot, 1v1

never mind Zur's Weirding, I missed the "any other player" part, which led me to believe you could pay the 2 life yourself

Wow, finding a card to avoid decking yourself in Modern and avoiding adding a color is really difficult.
Angel's Grace would be my first choice, but also Lich's Mirror and Possessed Portal are (mana expensive) options. Shared fate also would be nice, if you manage to also remove it before you pass. Or Laboratory Maniac, for an easier win condition.
Zur's Weirding also may work, if you manage to sneak a card like the old big eldrazi in your deck, or any other card with the same "hit the graveyard" effect.
That last one would work also with any dredge card, but then you would need to add green.
By the way, both green and white zubera are not so bad, the green one would replenish your side after a board swipe, that would be nice!

Glistening Oil can be used to remove the +1/+1 counter on Geralf's Messenger, if the need arise.
What about a Whip of Erebos? Not the best for this deck and a sure target, but at least it draws attention.
Or if you happen to have them, Initiates of the Ebon Hand can substitute the diamonds and let you play Darksteel Citadel

I've found out about this site only a few days ago. while at first every deck I checked was complete with description, name and "how it works", I felt the urge (damn me) to check the "new" section to see what came out of SOI.
And you are damn right. For {enter deity here}'s sake, it's just a few words.
I only wanted to say thank you, what you wrote may be a bit of a rant, but, as I've already said, you are damn right.
And you made me register, by the way ;)