LUNATIC ARMOR OF JAYM
This dark grey/black platemail with matching red-plumed helmet ought to be a big hit with all the anti-hero types. Not only does it protect as plate +2 but the user may surprise foes as if wearing non-metal armor. Mutli-class thieves and similarly sneaky characters may even Move Silently at no penalty. Unfortunately, the spirit of Jaym, the original owner of the armor, haunts the suit. Each month on the night of the full moon there is a 1 in 6 chance the armor goes on a rampage (treat as a wraith but AC 1). Anyone wearing the armor will be unharmed by the haunting, but they will be helpless to watch as the armor forces them to slaughter the innocent.
FACT: Scooby Doo has some of the best dungeons on TV.
One other bit from this episode that I have used in a crapload of dungeons over the years is the Secret Door Disguised As A Sarcophagus. Dig it:
I could probably do a lengthy series just stealing stuff from decades worth of Scooby Doo episodes. But since I've also got the Superfriends, Planet of the Apes, Johnny Quest and the animated Star Trek series, why limit myself?