1) ignorance..(not stupidity...I can tolerate people who can't help it, but not those who won't TRY to learn stuff.)

2) people (84.613% women) in grocery stores who stand in the middle of the asile, with one hand on their cart, blocking the entire asile while they contemplate whether to get Cream of Asparagus or Chicken Noodle today. I suspect some of those people are just stupid, so I don't yell at them.

3) Military types who refer to hidden weapons as 'cachets' rather than 'caches'...I suspect many of THESE are ignorant.

you did say 3 so I won't mention red-light runners.....or modern packages that require an axe to open.....or cute female news-readers who can manage to sound 'perky' when reporting on horrendous train wrecks...