For just plain coolness, I'm partial to the G3 (never had a real G3 but had a PTR 91). Felt like shooting a giant hole puncher, very satisfying ka-chunk feel to it, and I've just always liked them. Remember the heist shootout scene in Heat?
For a shooter though (I'm picky about accuracy) I prefer the AR platform, which is pretty common and boring these days, but I like the one I have which is a conglomeration of parts done the way I want them. For pure functionality it's a much better combination of accuracy and lighter weight than the 91, M14, etc, along with other advantages like triggers, optics mounting, tunability, etc.