Motorola StarTAC 7868. Threw it about 100 feet down a blacktop parking lot in a soaking rain once. You can still see the slight flat spot - with a good light and a magnifying glass. they don't make phones like that any more. (Mentioning the Nextel i58 wouldn't be fair - that's like comparing Volkswagens to Abrams tanks. Waterproof [not resistant, proof], drop-proof from 30 feet that I've seen, although I've heard of them being dropped further without a scratch, throw it against a wall and if the wall isn't solid, you'll have a hold in the wall. We used to throw it on the floor ot at a steel portion of the wall - as hard as we could - to demonstrate how tough it was. Picked up the battery and battery cover, replaced them and turned the phone back on.)
Current best? Note 3. (AT&T, though, so locked up tighter than Midas' purse.) M8 would be, but non-replaceable battery (I don't buy phones like that) and no S-Pen, although I could probably live with a capacitive stylus and a small tube glued to the Otterbox to hold it.