Doesn't matter how ridiculous, or how irrational, let's hear'em!
Here's a few of mine:
1. When people write (or worse, sometimes say) "congrats". If you're really that happy for someone TAKE THE TIME TO TYPE THE WHOLE WORD AND NOT SOME STUPID NON-ABBREVIATION ABBREVIATION.
2. Apples. They taste bad, people! But worse, that sound... UGH!
3. When someone doesn't have their credit/debit card ready by the time all their groceries are swiped. YOU LITERALLY HAVE NOTHING TO DO while the cashier swipes your food! It isn't that hard to think ahead two minutes!
What are yours? I know I have a couple others, but I'm blanking right now. I'll edit as they come to me.