Depends, whats available thus far?
I believe we have the poster boy for the game, the Dictator B for the Rach, already. Perhaps the lead Cav for each faction?
Adon - Chancellor/Challenger (Not the Ogre, he tends to polarize opinion apparently)
Almirithil - Kodiak or Grizzly
Templar - Centurion although I would make a case for the Crusader
Malvernis - I would like a Butcher B but again that's a polarizing choice apparently so a Pillager or Assassin?
Terran - Thunderbird or Katana looks cool. Tsuiseki just cause it's based on one of the greatest military aircraft of all time, OF ALL TIME.
RItterlich - Rhino seems to be the poster child for them. Although I like the squat, heavily armored "go ahead and gimme your best shot, I can take it." attitude of the Tiger.