I've not been keeping track with all the posts, I dunno if something similiar to this has been said, I doubt it though, but here it goes.
897. Pick up a copy of the MM2, and take every creature in the book and add all it's stuff into one HUGE creature. Everything like the ability scores, the feats, hit points, special abilities, spell like abilities, supernatural abilities, natural armor, special attacks, etc. Everything including the kitchen sink! And as the campaign goes along, have everyone refer to a legendary creature named "Ungeheuer Handbuch Zwei" (MM2 in German if I'm not mistaken, correct me if I'm wrong, I used a translator. Use some other language if your players speak German.) After a few sessions have the PC's finally run into the big baddy! And when they finally discover what it is, and have died to it, give them awhile to be so mad at you that they want to hurt you physically. When next session comes around, tell them it is morning and they have awaken in an inn after having the worst nightmare about something called "Ungeheuer Handbuch Zwei!"
To be even more evil, don't have them wake in an inn, but instead make new characters because they died!
Maybe it isn't that much to you guys, but it would be so funny to me, to see the reactions on my players faces!