That game is awesome for flow. Within minutes, you start dodging on instinct alone, and the world flies past you. My personal favorite though goes to F-Zero GX. If I play that for a while, I start dominating other games because I'm so keyed-up and focused. Too bad it fades :\

Link for those interested in Gunroar: http://www.asahi-net.or.jp/~cs8k-cyu/windows/gr_e.html