Big Rigs: Over the Road Racing, Ride to Hell: Retribution, The War Z and I'm not having too much fun with Aliens: Colonial Marines.
There are tons of games way worse, but they really aren't even worth mentioning, mainly because they were made on a budget of nothin by 1 person that didn't know how to write, design, or develop, coupled with the inability to compose music and make graphics.
OOOh, Back in the PSX days.. Deathtrap Dungeon was a festering little nugget. However personally I think I would go with (I cannot recall which this occurred with) PS2's Kessen or Unlimited SaGa. Which ever it was it was so horrendous that I recall palming the disc and proceding to snap it into shards (yeah big mistake btw) all to keep former stepson from trying to play it and thus defending an innocent living soul from having to endure such abomination. To hold something in your hand you know you paid more than 40 dollars for and without reservation or remorse obliterate it in an instant knowing in the blink of that eye the value of your investment shatters into so many more splinters than the actual disk had, tells you that it was an early PS2 experiment gone horribly wrong.
Though... there honestly have been so MANY clunkers over the years that my contributions are not representative of gaming and definitely in no shortage of equal and like minded company to chose from.
Some scars are seered in so deeply that no measure of memory bleach could ever wash them away.