Morphed wrote:some random powerups ideas

phase shifting - each bullet have 1/3 chance to go through you
healbot - you heal all nearby teammates
guardian - you shield all nearby teammates reducing dmg taken by 10%
speed - 20% more speed for you and your teammates
stealth - make all nearby teammates 90% invisible, you are not affected
hellfire - each explosion have 30% chance to set enemy on fire, damaging it over time
freezer - each bullet have 30% chance to freeze enemy reducing it speed by 30%
diseases - you spread disease to all nearby enemys that slowly damage them over time
living battery - you have 20% chance to shock enemys near you by electricity (pushing them back like laser or stronger ) and you rise dmg of all energy weapons by 30% near you
judgment - every1 that you aim, have weight incresed 2x make him unable to jump
i think that in ctf there should be more powerups that promote teamplay over 1 uber strong guy
These are exactly the kind of powerups which Warcraft and DOTA made famous and why it is so awesome! Here are some more which may be great for a FPS:
Lifesteal - You are healed for 15% of attack damage done.
Immolation - You are engulfed in a firestorm which does small damage to all enemies around you.
Hex - You can turn your opponent to a sheep for a short period of time. Sheep cant shoot or run very fast, but they do cry!
Swap - Use a ton of cells to swap places with anybody targeted. (Think about it)
Summon - Spawn a crazy bot in the targeted spot which will attack anything that moves.
How about this for stealth:
stealth - you are fully invisible but appear if you fire, have the flag or take any damage for any reason, so you may be invisible but you still have to dodge bullets and can't shoot anybody without being seen. Once visible you automatically begin to slowly fade away again.
I must say, however, that the reason it works in Warcraft/DOTA is simply that they are not ALL powerups so no 1 person can get them all. The best abilities are spread out among many classes so players NEED to make teams. Secondly, classes aren't as simplistic as "healer/engineer" , "sniper", "rocket launcher" and "infantry", nobody wants to be FORCED into a very specific style of gameplay. With a good spread of unit types and an equally good spread of offensive and defensive powerups DIFFERENT PLAYERS WOULD CRAVE DIFFERENT PICKUPS. Some would always need health but not ammo, some would always need rockets (because he starts with a hagar) but not bullets unless he got a MG ETC. I have seen these mechanics work well, just not in a FPS.