For lounging on the couch playing, I like the shape of an SG or a Strat the best. The contours, bevels, radii, and other comfort cuts make them ideal to play. Even a Gibson Reverse Firebird can be comfortable to play while lounging.
If I'm sitting in a chair with proper posture, I like the ES-335, Rickenbacker 330, and a Dreadnaught style acoustic the best.
While playing standing up, then I'm a bit all over the map. I love my Flying V, Jupiter Thunderbird, SGs, Les Pauls, Firebirds, Ricks, and Strats.