I have never particularly enjoyed the clarinet. I love bagpipes, I love digeridoos, I even can listen to the Vuvuzela, but I just can't do clarinets. 

Pedro steel guitars because they're always used in country music and I can't stand Country music save for Johnny Cash

Ukelele is painful to hear.

Human voice.

I don't generally enjoy a-cappella.

Saxophone usually doesn't sound so great from my experience, there's a lot of things that can make you out of tune with that instrument.

Turkish Oud - I think you need to be Turkish to play it. Its got a weird bent neck so if you carry it around it looks like its been in an accident. I bought one in Turkey (impulse buy) but it looked funny going round the conveyor belt at the airport as if damaged in-transit.

Bagpipes are awful sounding and i,m Scottish. Whenever you walk past a piper on the street (there are piper-buskers)  just put your fingers in your ears and give them a dirty look Irve Welsh style.

Any electric guitar that has three or more necks... Two necks are okay but what about these?: i.ytimg.com/vi/EAZdiJGWdfI/max…

Violin gets on my nerves.

Saxophone...

I can not think of one. 

 is this a backwards forum where the posts that are most recent are on page one and they go to the top instead of the bottom and the last page?    seems odd to be set up that way. 

The death whistle, unless when used as a prank or a scare tactic.
www.youtube.com/watch?v=I9QuO0…

I really hate the sound of a saxophone.

I think it's the only instrument which's sound I dislike.

I don't hate any musical instrument, but I don't like the xilophone's sound.

Cowbell  

Banjo.