3rd gen smith autos in 9mm, or .40
Anything in .40 caliber generally.
Pistols that I can't fit my fat fingers in the ejection port (CZ75, sometimes my P7 pisses me off in that regard.)
.38 caliber revolvers, I know that they are sweet, but I just can't bring myself to shoot a revolver, without it at least being a magnum or a big bore.)
Revolvers with 7 or 8 inch barrels, I own a couple and they just never get shot.
Taurus products. 'Nuff said.
Pistols that don't work out of the box, I won't mention any brands, because I'd be typing all night.
1911s with all the extended crap on them, and uber long beavertails, etc.
Compact guns that require a fierce grip on them to hit the x ring. (Some glocks, etc.)
Guns that aren't accurate. Don't waste my time.
That shouldn't really leave me with much, except that it does.
And that's a good thing.