[Galadriel55]

Honestly, I think that Isildur's Bane and Anduril are the finalists. Eorl and Ugluk are funny, but they don't match the first two. And between them, Isildur's Bane wins. Anduril can sure be helpful, but have you thought about all the times when the Ring has come in handy (though sometimes only for a short time)?

Isildur's near-escape. Gollum's hunting. Bilbo's escape from Gollum. Bilbo's escape from the Spiders. Being invisible to Smaug. Giving the Arkenstone to Bard. Seeing the Sackville-Bagginses come near and thankfully finding the Ring in your pocket. Making a dramatic disappearance, for Eru's sake.

And that's just some of the "handiness". I didn't mention Frodo and Sam at all, and they too had their times of finding the Ring "handy" when the moment arose.