I have a few irks.... (no particular order)
1) People who keep travelbugs
2) People who don't trade swag fairly and particularly those who replace it with rubbish, if you're going to take something then just take it, why bother putting an old raisan carton / train ticket / plain rock inside, it's not fooling anyone.
3) People who hide micros in areas where you could easily hide a bus.
4) People who copy and paste ridiculously long logs full of twaddle not even related to geocaching let alone that particular cache.
5) Armchair loggers - what is the point?
6) Certain long term cachers who make snidey remarks about new cachers and immediately dismiss anything they say about anything based on their number of finds. It doesn't cost anything to be polite and helpful.
6a) Particularly those who make derogatory remarks about 'smartphone cachers', why do we need to buy an additional GPS device when a battery pack for the phone will do?
Best moment ever was bumping into a geocacher at GZ with a very expensive GPS who told me I was searching in the wrong spot because his GPS said it was 30ft the other way and my phone was obviously wrong, turned out it was exactly where my phone said and his GPS was out, we continued along the trail together for a while longer and every time my phone was more accurate.
7) Cache owners who moan about logs not being full or detailed enough.
I can see why it may be annoying when it is a good cache but if it's a micro hidden on the back of a street sign in a big standard residential street what more do you want someone to say other than TFTC?
However, none of those irks stop me from enjoying caching with the kids.
We appreciate cache owners who put out any cache but particularly those who make interesting caches in nice locations.
Caches full of rubbish are annoying but we tidy them up and if I have enough on me to spare I will restock them.