never ever worn is a tough stipulation. i've worn things and quickly realised i hated them or they looked awful, but i tried them first. i was going to say a chemise - as in a slinky, silky vest - which i've never bothered with because without a bra my boobs are in the wrong place... but i had one when i was 14 or so.
oh - never worn for more than a few minutes proper flip flops, with a toe post. as a kid i didn't like them, and as an adult i have gradually noticed that my toes are a lot shorter that everyone else's, which is, i suspect, why i find them too painful to contemplate.