Suicune
Miltank
Chikorita
Marrill
Box legendary, the one everyone remembers as a roadblock, the starter that occasionally gets considered as "the worst ever" (and considering gym order, they're not far off,) and the one that spawned all the Pikablu rumors back before it came out
I kept trying to put Red Gyarados on here because that's honestly the only memorable part of Johto for me at this point, but it's just an angry gen 1.