Hellbringer on clan side :
-ECM
-Variable loadouts that span most meta categories, except for full-on splat/lrm
-High weapon mounts
-Good geometry (easier to learn torsotwisting on humanoid mech, than on snub-nosed mechs)
Thunderbolt or Grasshopper on IS side :
-Laservomit- and Snipingfriendly
-Good base quirks
-Tankiness
-STD friendly (and still quite quick) for extra tankiness
Honorable mentions for both sides :
Timberwolf - those loadouts ... hilarious
Ebon Jaguar - another loadout beast
Linebacker - less firepower than the 2 above, but holy speedtrap, THAT BASESPEED (also a pretty evil ERPPC carrier^^)
Summoner - Underestimated, still good, for either poptart-sniping or bonkers agile SRM splattage
Jaegermech - Want to run some rather cold IS Dakka
Rifleman - Did I mention rather cold IS Dakka already ?
Black Knight - Titanic mech in proportion, yet it can carry laservomit like the best, needs good map/situational awareness
Warhammer - Double Gauss ? No prob . Laservomit ? No prob . Dakka-laser mixes ? No prob . Nice chassis all in all
Archer - Some builds on it are pure ridonculousness, and I´m not really talking LRM´s here