Which creature from Monster Manual II have you used in your campaign?

[schnee]

I've used a few demons - the little ones that reflect damage rock (Jovoc?). I also like the one with the level draining gaze (Zovvut?).

The templates in the back rock also. 'Spell-stiched' for Undead let me pump up the turn resistance of my BBEG undead and make them a real fight rather than just a turn-fest for the Cleric. (He still got to vaporize a lot of mooks, though, so he's still happy.)

I plan on using a few others... the high-CR beasties in it are pretty good.

 

[Felon]

Encountered as a player:

Abeil
Desmodu
Fomorian (constantly confused with formians by other players)
Spawn of Kyuss

Used as a DM, or have plans to use in the near future:
Avolakias (conceptually cool, but poorly-designed)
Braxat (lousy illustration, but tactically they're great opponents)
Meenlock
Myconid
Spell Weaver
Spell-stitched template ("So, this evil 14th-level NPC cleric can use create undead to make ghasts--gee, that's really useful!")
Monster of Legend (the behir Grimlight in the Silver Marches will have this template when my players encounter him)
Scoprionfolk

I also have seen folks play desmodu and thri-kreen.