Grips and straight-arms
I think any grip is compatible with a straight-arm forehand:
Continental - Laver, Gasquet (?)
Eastern - Federer, Philipousis
Semiwestern - Verdasco
Western - Nadal
If you have a subscription to tennisplayer.net there is a ton of info on this style of forehand. One interesting article there, "How Rafael Nadal changed his forehand", by Jason Frausto, is especially worth looking at. It explains how Nadal shortened his backswing sometime going into 2008, which the author links to his improved results on hardcourts since. Nadal used to bring his hitting-arm elbow behind him on the backswing, which required him to then bring it back in front of his body before he started his swing. Now, just like Federer, his elbow never passes beyond the line of his body, so he can just fire from there.
I think this is a common hitch that develops in a lot of straight-arm forehands.