I few that come to mind...
Soul Fighter- A horrid, horrid Dreamcast game that suckered me in with the nice stills, yet, played, sounded and controlled beyond badly.
Sword of Sodan- A hack 'n' slash for the Genesis that looks good in screenshots, but assaults you with its piss poor qualities once you sit down to play it. The only real highlight is the opening song and some aspects of the graphics. Otherwise, controls, animation, sound effects, hit detection, gameplay, level design, enemy behavior... it's all just bad.
Big Rigs: Over the Road Racing- Over the road, under the road, through the road... dear God. This game sucks so much and on so many levels, it's the closest thing to a black hole in gaming.
Firefly- An Atari 2600 game that's just... pointless. Completely and utterly pointless.
Home Improvement- How this got made into an SNES game, I really don't know. That it got put into production once it was finished, is a crime.
Total Recall- A clear-cut definition of how to take a popular action movie, and turn it into a broken mess for the NES.
F-16 Fighting Falcon- It's a flight simulator, on the Master System. Slow, odd controls, you just keep shooting at jets, virtually no real graphics to speak of... someone had to have lost their job over this thing.