Puggo - Jar Jar's Yoda said:

Third vote here for Boris Karloff. A bit of a shame he became so typecast - he could have done anything. Although I think he enjoyed his horror niche a lot.

But he got typecast to a genre, not to a role, so we still get lots of variety in his great performances.

His great as a working class thug in "The Body Snatcher"

as an elegant but evil gentleman in "The Black Cat"

as basically a comedy role in "The Old Dark House"

as some Egyptian dude in "The Mummy"