personally, i've never seen an "ugly" cat, but i do have a soft heart for cats with disabilities or oddities. there was one cat at the spca that had a slight head tremor and eye sight problems. she was also a bit skinny, but i thought she was adorable. we would have adopted her, but since (at that time) we were first time cat owners, she was a little too play aggressive for us. if we ran into her again, we would most certainly adopt her! i think she was adopted into a good home though.
anyway, as for cats that are cuter--i have an even softer spot for orange tabbies!!!!!! I LOVE orange tabbies, i don't know why, but they make my heart melt instantaneously. maybe it's due to my childhood obsession with garfeild.