I have to agree with you on Drarry's. That's my anti-pairing too. I tried it out but it's almost always a squick for me. As for guilty pleasures. All slash is a guilty pleasure for me. Only my husband and my sister know that I read this stuff. My parents would literally have a heart attach if they knew.
As for genre, I love, love, love fics where Severus is looking out for or taking care of Harry, then as Harry realizes what is going on, love grows from it. However, I avoid any where Harry is under 16 because chan isn't really my thing. My favorite's are stories by lilyeyes and The Marriage Stone. I also love A Year Like No Other - I so wish that was a Snarry! I also like AU period fics (Victorian England and Snape = yumm!)
I have never read a girl!Harry, and would love to try one out if you have any recommendations.