The Rifleman (http://www.sarna.net/wiki/Rifleman) is a pretty classic design that looks a bit like the Mammoth Mark II (based on my google-fu).

It's not on the original list Seuss posted, but the Scorpion (http://www.sarna.net/wiki/Scorpion_(BattleMech)) is one of the few quad mechs that is used (never very well-liked or popular and it's not exactly common).