the little things in World of Warcraft

the engineering trainers in Ironforge's Tinker Town talk about their crazy inventions like a 100 foot turkey baster. Good luck finding a 100 foot turkey.

The 1 ring, which isn't as good as the 2 ring.

Sleeping or dancing on top of the mailboxes. Or, that one time when someone corpse dragged a tauren all the way to on top of the ironforge bank mailbox.

How you can spin your characters around like crazy on the character selection screen.

The troll witch doctor in Durotar

There is an abomination guard in undercity that wants a felhound as a pet. He says he will feed it and look after it.

The invisible ghosts that appear in the upper undercity entrance / courtyard. Its all ways fun to sit around there with my warlock and cast detect invisible on passing characters and watch what they do.

Glubber Bump.

/train, /cry, /sigh, and when I feel like doing something new, /em.

for those familiar with the cutscene from WC3 when Arthas takes down his father:in the throne room at UC, they even detailed the small streak of blood on the floor where the king's crown rolled onto the floor. AND you can listen to it while being in that room

Things like "YOU GOT MALOWNED!" in UD strath or "Kill the one in the dress first!" from nefarion (whatever he's called) during the rend event. I love hearing the hilarious dialogue that some places in the game have.

In Alterac Valley, on the Alliance side of the map, the road from the entrance has a steep incline when it meets the main road. There's a broken fence there, and a busted steam tank on the ground below.

I always liked that NPCs can mail you just saying "thanks" or maybe a little extra item.