Lets face it: sport bikes are awesome because they are essentially full-blown race bikes and racing is awesome. While that is true, the fact of the matter is that not everyone races and most people actually just use their sport bike for regular street riding. If you've ever taken a long trip on one of these built-for-speed bikes, it doesn't take long to realize the seat was not built for cross-country cruising.
Suzuki recognizes this and sympathizes with the bruised bottoms of the world with its Hayabusa Carbon Fiber Look Gel Seat. As the name states, it has a look that is reminiscent of carbon fiber. Seeing as how real carbon fiber is stiffer than metal, just sporting the "look" of carbon fiber is a good idea and actually pretty slick in the style department. The big selling point for this seat however is the extra padding. The gel padding provides some serious relief for your aching rear but isn't so massive that you can't ride your Hayabusa in the intended riding position. Suzuki also added a bit of custom styling with the Hayabusa logo stitched right into the side of the seat.
This seat bumps up the comfort level exponentially. It is intended for the 2008 Hayabusa but you can likely get it for other years as well. Your rear-end will thank you.
Here's a gel-padded bike seat for non-Suzuki riders.