The SEGA Dreamcast controller was the default controller that was bundled with the ill-fated SEGA Dreamcast. It featured a single analog stick, a 3D adapted D-Pad, a start button, four face buttons, and most notably invented analog triggers. As an attempt to advertise it being a "Next-Gen console", SEGA created two docking bay slots. They are primarily used for the Visual Memory Unit, though many add-ons utilise the jump packs.
The Dreamcast controller received mixed reception. Some thought it was a great controller, for it's imaginative build, tough enduring materials, and innovative interface (Mostly the VMU's) However, some thought the controller was over-sized. Others said the face buttons were to small.
As the standard start-up launch Dreamcast packs did not come with VMU's, the Dreamcast could not save games on launch.
In Sonic & SEGA All Stars Racing, certain characters can transform into a Dreamcast controller for their boat. This is probably a joke to one critic's description of the Dreamcast's shape resmbling ".... A speed boat....."
Sega Dreamcast In Wikipedia