If y'all don't mind, I'm gonna jump on the bandwagon with Dennis. I've always prefered darker more full bodied beers (both for cooking as well as drinking). Guiness is a great "old standby" and I use it frequently for chickens. Anchor Steam is also an excellent choice with poultry. Both of these impart a very definite flavor to the meat as opposed to some watered down house beer like Bud Lite or other such gruel.
Another one to try, if you can find it, is Young's Double Chocolate stout. Around here it is only sold in pint bottles, so you'll need to transfer it to another can. It's a little more expensive than some other beers and you may be inclined to drink it (cause its just that damn good) rather than sacrifice it to the smoke, but if you give it a try, I can pretty much guarantee that you won't be disappointed.
Cheers,
Brian