I think it does not matter out is on the feet. As long as the victims FEET are VERY TICKLISH! If I did have to pick one, I think I would pick flip-flops, because I live at the jersey shore & I'm around & get to see woman in flip-flops from May to the end of September & the right feet in flip-flops can be very sexy.
Well, tennis shoes usually make feet hot, sweaty and very ticklish when they're in them for a long time. Aesthetically, it just has to be the flip-flops. Tasty bit of footwear, them...
I went for tennis shoes and socks. There's something indescribeably cute about them if the wearer is also wearing blue denim jeans and even more so if they come off quickly.