The WTB Laser V Stealth. I like the drop nose for getting on the saddle without chamois suck. The drop nose is also more comfy for steep climbs when you have sit way up there in a very unnatural position. It's been good for both singletrack when I'm moving around a lot but also 50 mile dirt road endurance rides. Narrow enough to get all the way off the back and wide enough to sit on for extended periods.

http://www.wtb.com/products/saddle_laserv.html