I'm using 18-20g wire for all my non-audio wiring. As Daniel said, LED's take so little power that it really doesn't matter what wire you run, but the more flexible it is, the easier it will be to string through the car.
Hatch Nation #13 : Rally Revolution #13 : ROTM Jan '13
It's Bryan, not Brian
RSVT-170 Build in Progress
Derusting Rusty Build in Progress