Not a fan of Glocks - grip angle and styling just seem off to me. I'm still considering one as a carry piece simply for the ease of replacement, but its not a favorite of mine.
The first Sig that I fired was horrible - the grip felt enormous in my hands. It was a range rental, and I have no clue which Sig I tested, so I'll be giving Sig another shot in the future.
I personally hated the S&W M&P9 that I shot. I bought my XD-40 from the owner of the S&W - it was the replacement for his XD. Comparing the two, I can't figure out what he saw in the M&P.
As far as general gun dislike, I don't really like anything under .40 in an auto-loader, with the sole exception of .22. 9mm/.380 hold very little draw for me, but .22 is a great way to make lots of noise and plenty of holes quickly and inexpensively.
Personal love-to-hate gun - Beretta 950 .25 cal pistol. My coworker swears by one, wanted to make it his carry piece. I thought it was a cute little weapon - looked like a toy, but I figured Beretta would get the gun right. We took it out to the range and the thing locked up after less than a box of ammo. It was downright horrible to shoot. It may have been poorly maintained, but no amount of cleaning and oiling would get the slide to cycle smoothly. Talking him out of trusting that unreliable piece as his carry weapon was a struggle.