For me it has to be something open-toed, but here are my favorites:

Sport slides: I like the sporty look and I have a lot of memories of seeing girls wearing/changing into these when I played soccer growing up. Plus I like the way they frame all of the toes.

Birkenstocks: Specifically the Arizonas, these were popular when me/my fetish were coming of age so I'm sure that's part of it. They also develop really pronounced toe prints inside.

Tevas: This is related to the sporty look as well I guess, combined with popularity. I like the interesting tan lines they make too, Chacos are really nice for that too.

After that I think it would be other strappy sandals, flip flops, and then heels.

Guys, what do you prefer? Girls, do you like to wear your own preference or do you ever pick specific footwear for the purposes of pleasing your SO / teasing the foot loving masses out there?