YZF-R6 (1999 - 2002) review
Yamaha managed the same trick with the R6 as with the R1, caught everyone by surprise and redefined the 600 class.
Pros
Revvy engine with mid-range punch and light handling. 12 years on the R6 hasn't dated as badly as others from the same era.
Cons
Most have been tracked so do the usual checks when looking to buy.