A run-of-the-mill Legacy Zoo deck, with the 2011 twist: Green Sun's Zenith allows you to run more of a green-creature toolbox.
You'd usually want to use Zenith to pull up an early Nacatl or Tarmogoyf, a mid-game Qasali Pridemage for utility purposes, or a late-game Knight of the Reliquary. The hard part is, you really don't want to pull anything costing four mana or larger. Even Zenithing for three means you're paying four mana -- you could Natural Order for Progenitus for that, and what on earth would you rather have over a 10/10 with protection?
So, Zenith is a sideboard toolbox finder for games 2 and 3. Promising uses include finding Gaddock Teeg and Vexing Shusher. Mainboard, I'm testing Terravore as a finisher who can trample over Tarmogoyf and Knight of the Reliquary.
Interesting/fun/weird targets for Zenith might include Bloodbraid Elf, Boartusk Liege, Brown Ouphe, Cliffrunner Behemoth, Dosan the Falling Leaf, Essence Warden, Gaea's Herald, Gigapede, Glissa Sunseeker, Heartwood Storyteller, Hellkite Hatchling, Iwamori of the Open Fist, Kitchen Finks, Krosan Beast, Lhurgoyf, Masked Admirers, Mungha Wurm, Mystic Enforcer, Nimble Mongoose, Norwood Priestess, Ohran Viper, Ouphe Vandals, Realm Razer, Rhox War Monk, Sapling of Colfenor, Scute Mob, Sheltering Ancient, Spellbane Centaur, Skyshroud War Beast, Tamanoa, Tajuru Preserver, Terravore, Vengevine, Wren's Run Vanquisher.