The first notebook I used full-time was a 1GHz Titanium PowerBook G4, and while I used a bunch of iMac G3s and beige Power Mac G3 in high school, my part-time job at the time came with what I consider to be “my” first Mac — a Blue & White Power Mac G3.
(That’s my exact machine. I just got it back through an extensive set of trades on the Memphis gray market for old Macs.)