Re: Are there any other ships with a letter?
It may be the only one we ever heard about. But technically, the letter followed the registry number, not the name. The Enterprise-A, Enterprise-Z, etc., was just dramatic shorthand for the viewer's convenience. If we hadn't been watching, they would have just called them all Enterprise.
Curly: Moe, Larry, the cheese! Moe, Larry, the cheese! (Horses Collars, 1935)