Brooks C17 Cambium Carved (the one with the slot/cut-out).... 100% waterproof, designed for long distance/touring, plus you get a 10 year guarantee if you register the serial number on the Brooks website .... comfy straight out of the box

if you want leather.... Gilles Berthoud Aravis... the Rolls Royce of leather saddles but not cheap .... the Aravis has titanium rails

I own them both