You try to imagine what type of pony characters in other media are. (Did this for Team Fortress 2, a couple of days ago).
Scout - Pegasus
Soldier - Earth Pony
Pyro - Unicorn
Demoman - Earth Pony
Heavy - Earth Pony
Engineer - Earth Pony or Unicorn
Medic - Unicorn
Sniper - Earth Pony or Pegasus
Spy - Unicorn
I did this with a roommate for The Walking Dead
