If it's in a hero arena-like game, something like this maybe:
Shield: (mana shield)
Sticky Grenade: Throws a grenade at target point (targeting image radius 100), if it hits an enemy, it will stick to them and do lots of damage after a few seconds.
Spartan Laser: Fires a laser at target point after a delay of 2 seconds to charge it.
Warthog [ULT]: Hops on your warthog (would need a warthog animation) giving lots more speed and the ability to run over anyone you hit, but you can't use your normal attack.