[Mr_Majestic_76]

Demoman can do super jumps with shooting two sticky bombs at his feet and run towards and detonate (fly great distances).

Spy when disguised only carry the main gun of the character, never a secondary like knife broken bottle etc.

Pyro's never stay on fire, like others.

Scout's acts as two people on a capture point and not just as one as others (faster to take points).

Well most of these might be well known already , but newbies won't know.