Blastoise. Hands down Blastoise.
Because when I was young and got Pokemon Red, I was probably a little 'special'. I didn't see the anime yet and had no idea you could catch other Pokemon, even after the Old guy showed you how to catch them... So a decent amount of time later, my level 100 Blastoise finally managed to plow through the Elite 4 and Champion... In his honor, every Blastoise I own after has been named "Juggernaut", and I will occasionally do a juggernaut run in his honor, where i'm not allowed to capture/breed any other Pokemon and can only level the starter. I even managed to complete a Juggernaut Nuzlocke once! (Can't capture/breed anything, if it faints you lose)