Who do you think are some of the most chameleon like actors in flim and tv, young or old?

I'm just curious who others think are those actors that can really climb into roles like a chameleon and make them their own.

What I find interesting is over time, how many actors end up seeming to play the same character but only in different settings. And one interesting thing about this is how even the most highly praised actors can eventually seem to do this (Robert DeNiro is one that comes to my mind - earlier, his acting was quite diverse, but in later years, he has oftentimes has just walked it on. I think Billy Bob Thorton also exhibits this, with Clint Eastwood being the most obvious of performers that carry the same character into each role - ps, Eastwood is probably my favorite actor, so that comment isn't made lightly).

So, I'm looking for the really obvious ones. Tom Hollander (the UK actor) is one of these that comes to mind.

Others?