One of my favorite examples is Owen Burnett from Gargoyles. He's the personal aide of David Xanatos. He has a great deal of power, but it's more based on ingenuity and finesse than raw strength. This makes even more sense when he is later revealed as the fey Puck. Also I rate the stone fist incident as one of the best sacrifices I've seen.
Another is James Wesley from Daredevil. He's the right-hand man of Wilson Fisk. He creates a lot of obstacles for the heroes, arranges crimes regularly, and shields Fisk from trouble. When he kidnaps Karen Page, however, she kills him. Fisk is distraught over his death. It's probably the best villain-mourning-minion scene.
In my own work, I think I have to hand Best in Show to Socket. Recruited by Fortressa as a mechanic, Socket quickly develops a crush on her boss. But Fortressa has sworn off love! So Socket demonstrates that true love is when you put the other person's happiness ahead of your own. She shifts her energy into developing a strong friendship, because that is the kind of relationship that Fortressa can accept. And it works. They're great together. They're adorable. Socket is one of the main things keeping Fortressa from running completely off the rails. Just being around Fortressa and taking care of her makes Socket happy. D'aww!
So who are some of your favorite minions, and why?