Bread and butter:
Rescue, Sentinels, Gheist, Piranas, Jungo, Montana, Nightmare
(the clans people use most in elo. Doesn't mean they're the best, just most used. If you play elo, you will encounter them.)
Flash mobs:
Berzerk, Uppers, Sakrohm, Freaks
(they only come out when one of their cards is unbanned. But when they do, they come out in droves.)
Wall paper:
Junkz, Skeelz, Roots, All stars, La Junta, Vortex
(no one trys to counter them, they hardly get onto the banlist. They hang around, ignored and forgotten.)
Pink elephants:
Bangers, Ulu watu, Pcats, FPC
(very rare in elo. Doesn't mean they suck, just rarely seen.)