I like odd little things like squints, overbites, and gaps in front teeth (a la Madonna). Eve Myles, who plays Gwen Taylor in Torchwood, I think is gorgeous and she has both the teeth things - overbite AND the gap! Lovely. Who really makes me go seriously weak and gooey right now is Ruth Wilson, who plays the title role in the recent BBC series of Jane Eyre. She has an overbite, a sticky-out top lip and looks really cross - she has "angry" eyebrows that give her a sort of scowl. I love all those quirks. I really do feel overcome when I watch her on screen - but here's the thing about this notion of 'plain' or 'beautiful'. As befits the character of Jane Eyre, Ruth Wilson would I'm sure be considered 'plain' by most people. But while I accept she fits that accepted ideal, to me she is utterly, utterly, genuinely beautiful.
About the plain/funny vs beautiful/dull thing, plain but funny for me every time. I'm hoping Rubyrose was joking when she suggested we men aren't hardwired to think that! (Or, at least, perhaps the men SHE knows aren't).
Dull, unfunny people, male or female, are one of the biggest turn-offs.