Most of my family members aren't really "into" LOTR, so often our nicknames for characters are less than flattering...
Sadly, unless I use the nicknames, they have no idea who I'm talking about.
In our household, Boromir is The Human Pincushion, also Mr. Pessimism a.k.a. "Twenty Reasons Why This Quest Won't Work."
Galadriel is just "That Creepy Elf Chick"
Eowyn is "If He's Not From My Village, Then I Love Him." We have some long nicknames at our place.
Gandalf is Gandy, Gimli is Gim-Gim or Gims, Aragorn is Arry or Gorn, Faramir is Far, Boromir is also Bor. (You know; the average nicknames)
Denethor is The Human Torch.
Sam is "The Smart One," Frodo is "Tell Me What I Shouldn't Do, and I'll Go Do It" or just "The Moron."