For NPCs, most will be standard. A few that are PrCs, tend to stand out in player's memories preceisely because they were not standard. Nothing like seeing the player's reaction when one guy they're fighting expalins his own style of combat and the player's realize that he's a warmain as opposed to a fighter. Not a lot of difference but enough to make the player's change tactics a little to more hit & run.
In terms of PCs, heck, anything that I feel fits my character concept. For most, I don't have to worry about it as there are so many feats, skills, PrCs, etc... that I tend to find one I'm interested in and stick with it, but for other aspects, like say spells for a spellcaster, the more the merrier.