ScudChuckle

This AddOn causes your character to emote occasionally during combat, e.g. whenever you land a big crit or when you kill a powerful enemy.

The settings panel lets you set whether your character is jolly vs angry (will they laugh and chuckle more, or are they more of a roar and yell kind of person), and whether they emote only very occasionally or all the damn time and they never shut up and everybody hates them ugh (author accepts no responsibility for you annoying everyone around you if you turn it up that high).