With so many cards that generate or synergize with Treasures, its easy to get an instant benefit out of your Goldspan friend
Pretty strong stuff
Balefire Liege, Blinking Spirit, Tradewind Rider, Spirit of the Night, Spirit of the Hearth, Azorius Herald, Bloodghast, Nether Shadow, Nether Spirit, Nether Traitor, Krovikan Horror, Celestial Crusader, all of the Spirit avatars like Demigod of Revenge, Primordial Sage, Dimir Infiltrator, the muse cycle like Windborn Muse and Seedborn Muse, Eternal Dragon, Ghost Council of Orzhova, Guardian of the Guildpact, Swans of Bryn Argoll, Wall of Reverence, Karmic Guide, Midnight Banshee, the Phantom creatures like Phantom Centaur and Phantom Nishoba, the Rusalkas, the Eidolons, both Spirit Guides, Sovereigns of Lost Alara, Spectral Lynx, and, of course, Will-o'-the-Wisp
Sort of Feast for Crows can be used to eliminate problematic cards from your opponents hand, deck, and cemetery
Void Rend A simple but effective Esper card to get rid of nonland permanents without fear of it being countered
The sprite is the only free, repeatable source of Surveil, but a 2 mana 1/2 flyer gets run over in way too many match ups
