You know what the worst thing is? We can't do impressions of him anymore. Basically, every impression kinda needs to be a rape joke now to justify it, or worse, every impression is a rape joke by default. Rape jokes should be a choice, same way sex should.
Sucks that he's forever tainted, but not as much as what happened to the women he wronged.
Short Answer: My favorite thing about Bill Cosby was other people's impressions of him. Those days are gone.