You're gonna spend a lot of time in this seat, so better make it a good one. Brooks England has made its durable leather saddles for years, and the B17 Narrow is perfect for fixed gears, because it's built for speed and will develop a nice patina. If racing's more your forte, you can't go wrong with Selle Italia, whose saddles are vented and feature padding for comfort. This particular model, the SLR Gel Flow, is infused with a silicon gel.
Brooks B17 Narrow
Buy It Now at Brooks England, $114
Selle Italia SLR Gel Flow
Buy It Now at Bikeman, $172