Orchestral strings played pizzicato. These have been thoroughly spoiled for me by being used "humorously" in reality TV programmes, where they're typically background music for people poking around French farmhouses they're thinking of buying, or failing to coax the best from a flan. They've nearly gone the way of the trombone and tuba, now for ever associated in my mind with the "comedy" parts of natural history programmes ("Look at the baby warthog as it learns to galumph around the water hole! Oompah, oompah!"). Yuck.
Pretty much anything played in 3/4 time. Yes, I know this covers an awful lot of territory. It really comes down to my being repelled as a child by the kind of grown-upness for which nineteenth-century Viennese waltzes were to me a metonym. Grown-ups twirling in pearls and thinking they were so bloody sophisticated when all they were was boring, boring, boring. At some point my brother pointed out that not everything in 3/4 was by Johann Strauss. "What about the opening of the Eroica?" he said. Fair point, but then that is my least favourite Beethoven symphony. (5 is the shit, except for the second movement, which is in lumbering 3/4: how I wish he'd used the second movement of number 7 there instead!) I admit 3/4 can be okay, but mostly when it's not at all insistent, or when it's so insistent as to become deliberately grotesque, as here or here.
Irrational musical loves.
The banjo. Just can't get enough of it. Can anyone?