There are certain cars that, in my eyes, tell me that some people just don't care about the car itself, only the image the car carries.
Perfect example: The Prius. That is all.
Another example: Any of the super-mini cars that are trying to sell. I understand England had an epidemic of itty-bitty one-person Gee-Whiz cars not too long ago. At the same time, I remember the Smart Car was selling quite a bit in the US, and it's the same damn deal.
I have a prejudice against anyone who has even the faintest whiff of douchebag. I know it's a very broad term by now, but it's just an entire clique that I cannot stand. Wear your hat backwards for no reason whatsoever? Actually physically pop up your collar? Listen to meaningless rap-hop? Play NOTHING but generic brown-and-gray FPSs and Madden while reviling virtually everything else? These are signs of douchiness, and you can kindly suck a big bitter pickle. Do you walk down the hall, playing your shitty meaningless rap-hop out of the shitty speaker on the shitty phone you bought because your shitty friends bought it too? I hope you choke on the pickle.
Hipsters. There's something about them that I can't quite place my finger on that I don't like about them. Actually, in that vein of thought...
Apple users. HATE. THEM. If I see someone with a macbook that they're genuinely, defensively proud of, my opinion of them goes down a little. If you have so much as an iPod, chances are good that we aren't going to be good friends.
People who care a lot about celebrity news. I don't give a flying crapcake who had a wedding, who adopted a baby, who got drunk, and who's gone through the revolving door of drug rehab this week. If it's a really good actor/musician that dies somehow, I'll pay attention. If it's someone REALLY good, I'll even mourn them for a minute. When George Carlin died, you'd best believe I felt it. When Michael Jackson died, I cared only because nobody would shut the hell up.
If you're getting excited because some mediocre-flavor-of-the-week pop star decided to have a girl/boyfriend, you need shots.
So, yeah, those are my prejudices. I think I've met examples of all of the above that turned out to be great people, but I've met enough people that fit the prejudicial bill well enough for me to carry on with my pre-judging.