I thought the mini private key format, used for Casascius physical bitcoins should rate a mention here, because it's basically a SHA256 brainwallet... but with a randomly generated passphrase.
Given that the random passphrase length is 22 characters (early version) or 30 characters, the chances of brute forcing it are still virtually nil, but technically, it is less secure than a standard key, in particular because 99%+ of the tries can be discarded after the first SHA256 hash.
By the way, funds have been sent to (and promptly swept from) the address associated with the sample mini private key on that page: