I use either a Minox 35GL, a Yashica Electro 35GSN (but I'm going to sell that), or my lovely Olympus 35SP. I think I'd be too self-conscious to use my SLR (and I'm impressed by some of the gear people in this thread have used on the street), but the eccentric WTF-factor is probably high enough that I reckon I could get away with using my Zeiss Ikon Nettar folder. Must give it a go.