Excluding all of my worthless sports games, I have a few that could basically be considered "worthless". Space Invaders for the 2600 or Super Pitfall for the NES, for example. I'd be hard-pressed to get a dollar for either. Space Invaders, on top of being fun, is noteworthy because it's the game that really popularized the 2600. Super Pitfall is noteworthy to me because it was one of the few games that I had for the NES as a kid, I bought it purely due to name recognition, and I played it even though it was and still is god-awful.
Chris