I saw this thread, and the first thing that popped to my mind was Candle of Invocation.

Unlike other poorly written things that exist in 3.5, Candle of invocation is worded precisely. It explicitly details what it does, although it hides the truly broken part after an end-of-page break.
Things like Iron Heart Surge or Drowning, there's obviously a hole. Something the DM needs to Rule Zero in. They are BADLY written. One line of text would fix either one.

Candle of Invocation? Oh no. The writers knew EXACTLY what they were doing. The CoI is a piece of Dev Malice against all DMs, a piece of aged cheddar that doesn't hide what it does, it just puts it after a wall of text to make lazy or inexperienced DMs think it's OK.

Munchkins cackle out loud at gaming tables when the oft-asked question of "Can I buy this?" is answered by a "Yes" from the DM after cursory examination.

The Dust of Sneezing and Choking compares, but is not nearly as game-breaking. Sure, your lv 5 party can take out a Great Wyrm Black Dragon with it, but you have to actually find the dragon. CoI? You gate in something with Wish SLI, then wish for some dust of sneezing, then wish to be transported to the nearest safe location within throwing distance of a Great Wyrm black dragon.

It's not just cheese, it's the entire omelette, besides.