Music concerts.
I absolutely love music. But live music just doesn't do it for me generally. Every time I go to a concert, it's not long before my feet hurt, I'm tired/bored, annoyed by drunk dickheads and I want to leave. I enjoy the music, but I'm always stood there thinking that I could quite easily be enjoying the music, elsewhere, in better quality, and without feeling so ****** off otherwise. I can't remember the last time I went to a concert where, come the end, I wasn't actually relieved. Everyone else is shouting for "one more song!" and I'm praying they don't bother.
I think the only concerts I have genuinely and properly enjoyed from start to finish have been the few Muse gigs I've gone to. Not only as they are one of my favourite bands, but they do a cracking live show. But even then, I think I was perfectly satisfied by 1.5 - 2 hours of music. Which is why when I hear people get all misty eye about rock concerts that went on for hours and hours, I think to my self, I can't think of anything worse.