Well, my favorite was the nova cat... it had a couple of defects but i played MW for YEARS and i found myself always using a MadCat(Timberwolf) a NovaCat(Rifleman) or a Daishi(DireWolf)... The madcat packed less ER lasers then the Nova cat but had LRM's in addition. The Daishi was just a big, slow cube of ROCK but i found it to be quite weak actually, skilled players only needed 3 shots to take a Daishi down, because of it's HUGE 'nose' it was easy to hit the center torso 3 times in a row, in 90% of the cases that was enough to take it down.... still, the daishi could carry a big variety of weps like 2 big gauss', ER lasers, LRM's, the whole deal...
The nova cat was agile, very powerfull because of it's 7(!) ER Lasers... like i said before, the arms were easy to shoot off which made it a bad clanfight-mech (because the opponent stipped u and left u for useless the rest of the game) but for a skilled player it was a very powerfull mech!.... you needed some skill tho because it felt like you had only one weapon, 7 lasers ... BAM! all at the same time... you needed to make sure every shot counts and went exacty where you wanted it to hit your opponent.. To that, i think the nova cat is the most impressive looking mech with its HUGE 5 barrels, it's broad shoulders, enormous arms and it's "Cylon" looking head...
Nova Cat 1st
Mad Cat 1,5st
Daishi 3rd