I recently started playing halo 2 (which so far is not as good as CE or 3) and what intriged me was on the arbiter missions you can constantly use active camo (instead of flashlight) and it would have to recharge. (Oh and don't start a flamewar about which halo is better).
Now what if equipment were more like that, here's some examples:
Jump pack: Gives you jet pack that lets you do quick boost and then recharges. (Brutes have these in H3).
EMP pulse: Lets you do an EMP using your shields energy. Works like the power drain, but you loose your shields as well. This would work for team based games. On CE you do this when you have to destroy the three reactors.
Visor: (from ODST) Let's you see enemies in red, weapons in yellow etc. Also it should let you see invisible enemies.
Flashlight: From H:CE, Turn it on/off and it recharges.
Remember that these do not neccesarily have to be used in MP.
Flashlight would be useless in MP, but it would be nice to have it in Campaign and custom games for nostalgic reasons.
Also there could be traps like the grenades that shoot up on sandtrap or deployable turrets which would be good for firefight.
Thank you for reading and feel free to post your own equipment ideas.
[Edited on 09.16.2009 1:55 PM PDT]