Reskinning Monsters: I do this *every game*. The Monster Builder allows me unlimited opportunities take disparate powers and abilities and apply them to my ideal antagonist. A piece of Minotaur here, a dash of Orc there, add a hint of Hobgoblin and voila: a perfect War Ape in the service of my Mad Scientist.
When I am a player, I reskin constantly. My Tiefling Warlord, for example, doesn't simply shout encouraging words and occasionally point out his opponent's weaknesses---he invokes the forbidden, hell-born pacts of his ancestors and lends his companions infernal boons. He opens a conduit into Hell itself, momentarily granting the fighter the strength of a Pit Fiend, or the Ranger the accuracy of a Spined Devil. All the better to smite those foolish enough to oppose them