The Comfort Strapp. I got my first on in 1997. Before that I'd managed a guitar store and was on an endless quest to find the right strap. After that I still would try some (I had that goofy D'Addario "Air Strap", and I tried Fender's version of the neoprene strap that Neotech makes) and nothing works as well as the real Comfort Strapp.
I have a milk crate full of straps, thick leather, wide leather with sheep-skin padding, wide ones without padding, neoprene, one cool looking one with a six-inch wide pad, Levy's, etc. I only use Comfort Strapps on my basses and have three of them.
John