This might get me murdered...but Arrested Development. My buddy had me watch an episode once and I didn't get what all the hype was about. In my defense it was a random episode and that's a show you sort of need to from the beginning. Not because the story is complicated but you won't get any of the references.
Well he tried to get me into it while it was on the air and I couldn't. Well years after it got cancelled I gave it a shot and by now I've seen each episode 3 or 4 times.
Ooo good one =D
Ironically enough I couldn't stand RPGs when I was a kid, I was a little graphics whore and the top down perspective and small characters looked unappealing to me.
Around 13 or so I hated Punk Rock, I thought it was cheap and talentless crap. Around 14 it changed my life =D
More recent-ish - Country music, not the crap on the radio, I still think that's an abomination. I'm talkin' about some old school Johnny Cash, Hank Williams (Sr., not the Monday Night Football guy), Buck Owens. Similar to punk really, simple songs, maximum expression.
I guess these are more things that I never bothered to give a them a shot but when I did, I found awesomeness. Other than that, I'm pretty consistant and stubborn in regards to things I can't stand =D
I'm with you there. Old country has been growing on me.