Hmmm, depends on how old we are talking about.
If we're going back to the original Disney/Warner/Hannah Barbara then probably Woody Woodpecker and Droopy would be my faves. Marvin the Martian and Ole Sammity Sam get best supporting character votes.
A bit more recent and it's Thundercats and Jayce and the Wheeled Warriors.
More recent again, and I'm ashamed to say that Yu-Gi-Oh got my attention. I've not idea why I enjoy it, but back when I had TV, if it was on, I had to watch it. Bizarre
. Maybe they built in some sort of addictive subliminal message or something