Mine has to be either Scott Redding winning the british 125gp, Laguna Seca 2008 or Motegi last year!
I started watching racing the year Neil Hodgson won the WSB - began watching that, but quickly switched to watching Moto GP when Rossi made the move from Yamaha to Honda in 2004.
Will probably start watching some more BSB this year as my insurance company offered me cheap tickets plus a load of other goodies for going...