The highest likelihood of causing a crit I think happens to be LBX. IIRC... followed by MGs (generally, because you stack them in bulk, and they fire multiple shots quickly).
The lowest probability... is ones without crit bonuses or are difficult to stack, but also do less than 10 damage per shot. This would include AC5s/UAC5s, AC2s, LBX, and Clan ballistics (outside of the Gauss Rifle) and others that I can't think of the top of my head.
Aiming for crit damage is a wasted thought... going for big damage dealers like AC10s, AC20s, PPCs/ERPPCs, Gauss are far more reaching for destroying DHS and other stuff.
The weapons that generate the most crit damage are often times bad for damaging mech external armor.
Edited by Deathlike, 11 July 2014 - 05:00 PM.