The various "Holier than thou' brigades.
As of recently, the airsoft variety are really starting to grind my gears.
Don't like people using hi-caps? Grow up, shut up and go to a milsim game.
If it's not a milsim game, people are well within their rights to use them.
Not everyone who uses them sprays like Rambo. Some use them for practica reasons (like not having to constantly go back to the safe-zone to re-arm) or economic reasons - magazines aren't cheap, especially if you find you've just spent £19 on a magazine that doesn't fit/feed in your gun.
Midcaps don't equal 'l33tsk1llz'. I've seen plenty of people who spray whilst using mids (and even lows

), using all 20 magazines up in the warm-up game, which lasts 10 minutes...
My flatmates. I love 'em, I really do, they're a great bunch of girls (didn't realise my accomodation is predominantly a nursing/medics block, there's me and 1 guy with 7 girls in my flat) but, they've done something that infuriates me.
I clean up after myself. If I mes up the kitchen, I clean up right away. I vacuum the hall if needed. I empty the recycling. If I return from a night out and spill drink in the kitchen, I clean it up first thing in the morning. Hell, I've cooked for them a few times.
Do they? Not really. On a few occasions I've cleaned the kitchen after they've had a drinking session (Southerners can't handle their drink), or come back smashed. So they've created a rota to make sure everyone does their job. Only, I've now gotten extra stuff to do, stuff I already do... Great...