Oh god, we could be here all day.
I think the best one was a few years ago...I get a call from a customer...this is kinda how it went:
Customer: I need to get my CPU fixed.
Me: What seems to be the problem?
Customer: My cup holder broke.
Me: ...your what?
Customer: My cup holder. I set a cup o coffee in it and the dang thing just snapped right off there.
Me: ...well, bring it in.
At this point, I think it's just a prank and no one will show up. But sure enough, a guy walks in the door about 30 minutes later...
Customer: I'm the one that called about my cup holder.
Me: ...ah.
I take a look at the cd drive, and the tray was snapped right off, and there was definitely a little coffee splatter on the case. Turns out the guy set a stryrofoam cup in the cd tray...and it snapped off.
So I sold him a new "cup holder" for 50 bucks. Though I told him what it was actually for.
Customer: So, I can't get a cup holder for my CPU?
Me: Nope. They don't make them.
Customer: Well shoot.
Just picture him talking with a southern accent the whole time.
Yeah...not much topped that in my years at the shop.