Yes, all have good points there. However, there is somethin i find useful about the flash light in a low light area: you can see the signal even if you do not look at the person.
Rondog, you r right, the look up down thing is a bit hard. I think melee is a good one though, especialy if ff is off, then you can melee someone pn your team and they will know you signaled them. Shooting them may be better thanthins though....