I was going to say drow, but they are not monsters anymore, like orcs.
My players are sick of cultists after playing PotA.
I also think that overusing monsters depends on what tier you are in. Low levels tend to have goblins, kobolds, and blights. Mid levels start to have trolls and giants, while high level PCs encounter demons and dragons.
I always found it strange that goblins morph into giants as the PCs gain levels, since they never encounter them anymore. At least 4e had goblin minions that could be 8th level.