This may be a tough one, or maybe not if you bought some FFE products during the D20 glut of games. I bought my FFE products as part of an eBay package deal at like 3 bucks on the book - so the stinkers stank less due to the cheap buy in.
No, my all time winner of "Worst RPG Product I Ever Bought" is also the only one I ever returned and demanded a cash refund on - Monster Coliseum for Avalon Hill's RuneQuest 3 game. Oh my fucking God - this turd was expensive back in 85/86, when all my income came from a $8 a day off the books job. What can I say? I was 18 and in college ;)
The great thing is, I got my money back (although it may have been store credit) and I saw that box remain on the store's shelves until it moved locations a few years later.
I don't recall what I was hoping to find when I opened the box, but it obviously wasn't what I expected. There was nothing to use in it for my novice RQ3 campaign.
The Minotaur for Old-School Essentials
*Requirements:* Minimum STR 9, Minimum CON 9
*Prime Requisite:* STR and CON
*Hit Dice:* 1d10
*Maximum Level:* 8
*Armor:* Leather, including shield...