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