I have little bitty, narrow feet. I like the Nike sandals that have stretchy bands to hold them on. Otherwise I'm in danger of walking right out of my shoes, since casual shoes don't typically come in narrow sizes.
I found some nice plastic slip-on sandals at Walgreen's, of all places. (Not thong sandals; I can't stand the feeling of that little thingy between my toes.) They are called Okabashi sandals, and they are surprisingly comfortable. Great for schlepping around the hot tub. These come in sizes from teeny to immense, and I highly recommend them for cheapness, comfort, and disposability. If you step in a piece of gum, you just throw the shoes away and get some new ones.