@freemo
You need to have .380 on this list. Ruger LCP's are perfect for when one finds it unwise to carry a "real" gun. I have also seen some compelling evidence that says caliber isn't all that important when defending yourself from other human beings.
@IAmErik .380 and 0.40 both deserve to be on the list honestly. Sadly i was limited to 4, and these are the 4 that are my top picks so I went with it.
As for the importance of caliber... in most situations I'd tend to agree. Even a 0.22 is pretty deadly at close range, at least enough to incapacitate... But there is important differences like penetration potential which can be fairly critical when you consider other factors (like collateral damage).