It's simple, just a command to light someone else's cigarrette with your own lighter. It'd be quick and boost RP!
"Got a light, handsome?"
"Hey boss, you need a light?"
"Light up my Black Deth or I'l detonate this bomb!"
I like this idea a lot! How many action movies do we see where guy A is sitting, shot to hell and back, got that last cigarette in his mouth and the enemy or his buddy lights it up for him? There can be some cool moments both for regular RP and for like enemy-to-enemy RP that comes out of being able to light someone else's cigarette.
It has some uses in very niche circumstances. I understand the value of it, but I don't see it being worth the coding when it's not a frequent situation and can usually be handled by existing means. If the person is too weak (fatigue run out) to actually do it, the person could light the cigarette themself then hand it to the person, and again RP that it was put in their mouth and lit for them.