Well, Blizzard doesn't always do the most original thing, but what they do they usually do really well. It would be just like them to take a somewhat-cool idea like achievements and really take them over the top.

I like that idea of user-driven achievements, too. That could be the original slant to this whole thing that turns it up to 11.

Off the top of my head...

Hogger Must Die: Killed Hogger at level 1.

Forever Young in Neverland: Stayed the same level for over a year (for all those bank alts, PvPers and parked alts)

Pacifist [Rank (x)]: Reached level x without doing any damage to enemies.

Pugelist [Rank (x)]: Reached level x without equipping a weapon.

Lemming Award (thank you Goldeneye!): Died 1000 times by fall damage/self-casted Hellfire/self-casted Engineering gadget/etc.

Notorious Ganker: Killed 1000 players that were over 10 levels below your level.

The Friendly Ghost: Ressurected at the Spirit Healer 10,000 times.

Philanthopist: Gave away 10,000 Gold via trade window.

Monster Combo: Killed 50 or more enemies within 20 seconds. (for the AOEers)