A flashlight can be very handy.
Imagine this, you're having a night skirm or you're walking through a dark building.
It would be handy if you could see something.
Stroboscope functions can disorient your enemies, for an added advantage.
In short, its a multi-purpose tool, that surely cannot be missed in an Airsoft kit.
Lasers can point out where the BB would hit. This is often handy in the dark.
CAUTION! Take in account your local law regarding lasers! Consult your law regulations before you buy/mount a laser!