Gil-galad! He was strong enough to fight Sauron himself so I think he's an ideal choice! So what if he's dead, this could be a "what-if Gil-galad survived?" Or perhaps he is sent back by the Valar (like Glorfindel) to deal with the Ring because of his experience with Sauron personally?
I will admit though, I am extremely biased. Gil-galad is my favorite Tolkien character, even more so than Saruman!
Gil-galad is already well implemented in the Last Alliance spell, a great reference to the Second Age.
After Gil-galad was killed by Sauron, his soul departed from the World and arrived in the Halls of Mandos in Aman.
We thus don't know if he is still mourning there, or if he was reborn in Valinor; I believe that he was granted the rebirth in Valinor for his epic deeds, but, in both cases, he can't leave Aman, as everyone else who lives or was reborn in the Undying Lands.
Glorfindel is the only exception