I would enjoy a Crucible playlist with Nightfall-Style modifiers like the Elemental buffs or Juggler. It would be a pain in the ass, but it would be interesting to use PvE tactics in Crucible. A game mode with the Boundless Light buff and all weapons disabled, like Mayhem, except without all those pesky heavies and Invectives. Also an Exotic acquired from actions performed in a Daily Crucible Activity. Maybe an extremely rare drop from Salvaging a Relic. Melding a little PvE and PvP would be an interesting combo.