1) Bandits. Very versatile, with only a couple of annoying abilities (Divine Shield). Can be used for many triggered events (transmissions, ambushes) to make enemy encounters feel more alive.
2) Gnolls. Not as versatile as bandits but are satisfying to kill, can be used on many maps and don't have any annoying abilities (like Magic Immunity, Slow, Flying, Possession).
3) Murlocs I guess
I hate trolls. Every troll feels the same unless it's a Priest.
Golems are OK, but the larger ones are annoying when you can't use spells on anything else.