Who was the best/worst SecDef in US history?

Rumsfeld stated: Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know.

Had a discussion on the blog and the revolving door we've seen at the top of defense depts (mainly in the US and UK) came up.  To make a short story shorter, my response was that I was of mixed feeling on the subject.

I'm stuck like stupid on Rumsfeld's term under Bush and the nonsense (I consider it idiocy) that he was spouting at the time.  On the flip side there was Mattis and while he will never approach God-hood with me the way he has with others, in the short time his focusing on actually doing the hard work of defending a great nation and ignoring idiocy was refreshing.

But that's all recent history.

Who was the best and worst SecDefs in US history?