Berserk
Increases weapon rate of fire speed. Additionally, it will also supply full ammo for all the weapons you currently have.(Best for Automatic weapon usage)
Slow Field
Slows enemies in a 3m radius, except this sucker’s portable.(Could be by teams to slow pursuing enemies going for flag carrier)
Jump Boots
Boots that allow players to jump higher around the map opening up new routes temporarily. These boots are activated by double jumping. It is also possible to dodge-jump if and only if you have these boots.(Double-jump a more balanced and tactical jetpack)
Those are pretty much copied from UT, alot of stuff from that game could work in Halo.
My unique power-ups I came up with tailored to Halo:
Rifle-men- Your shields do not regenerate for 30 secs, but your damage is multiplied X2. Best if used by a sniper, or from in cover.(Kind of a play on the damage power-up)
Adrenaline- All player movements/actions are increased X2 for 30 seconds.(Basically an improved speed boost)
Explosion- All explosives and splash damage increased for 30 seconds.On top of this, if you die you will explode and cause heavy splash damage on nearby enemies.
Elementalist- Using Human,Covenant, and Promethean weapons will have different effects.
Human- Bullets temporarily become fire, applying powerful DOT effects for half of that weapons damage.
Covenant- Plasma temporarily stuns enemies and all vehicles, especially useful in CQB and for fleeing enemies.
Promethean- Temporarily gain chain lightning effects on near by enemies. Useful on groups of enemies/near enemy bases.
Some of those ideas are pretty unrealistic, but I feel like some of those could work =)