On the subject of Xenakis, Sorabji, etc.; I do not like their music (maybe a little Sorabji every now and then..), but I do respect it. For example, I would never, under any circumstances, listen to the music of Finissy. However, for a person to be able to imagine, write down, and play that music, is an incredible accomplishment. Just not one I'd listen to.
However, more on topic, Fur Elise, Moonlight Sonata (mvt. 1, anyway) are annoying to me. Then there's any/everything by Richard Kastle, which makes me want to jump into a pile of large, hairy, venomous spiders.