There are two ways to look at this. I'm pretty sure the OP meant omnis from TRO 3050, but you could also look at omnis that were around IC in 3050. I'll do a lineup of each:
TRO 3050:
Light- Adder, because it's like a baby assault mech. Also, the Kit Fox needs more armor, the Firemoth is too niche, and I don't like the Mist Lynx's configs.
Medium- Nova, because the Stormcrow is too popular for me to pick it, and the Ice Ferret and Viper's configs are weird.
Heavy- Mad Dog, because I like its configs the best, and the Timber Wolf is too cliche, the Summoner's configs annoy me, and the Hellbringer is for nuts like JHB.
Assault- Gargoyle, because style points. Also, the Dire Wolf is too easy to pick, I don't like the Warhawk's configs, and the Executioner is for crazy folks.
IC 3050:
Light- Arctic Cheetah. Seems like the best blend of speed, firepower, and armor to me. Though it is worryingly light on that last one.
Medium- Shadow Cat. As above, and I like most of the configs, though I'm not a huge fan of MASC as a rule.
Heavy- Ebon Jaguar. Not to say it couldn't be improved, but it's better than the Mad Dog and Summoner. Not the Timby, but as above, the Timby is too cliche. And I like its configs.
Assault- Kingfisher. The ultimate clan zombie-omni, and the configs are generally at least solid, if not awesome.
Notice a trend here? TRO 3058 was a beautiful thing.