Frodo went to Mordor and brought back Aeglos, Belthronding, a Cavetroll, a Dúnadan, Elessar, a Fell Beast, a Giant, Maedhros' severed hand, Ithildin, a jibbet, King Théoden, Lobelia Sackville-Baggins, a midge, Narsil, the One Ring, Pipeweed, Quickbeam, Radagast, the Silmarilli, Túrin, Ulumuri, Vairë, a White Tree, the Yellowskin, a chunk of Zirak-zigil, the Arkenstone, a Black Rider, Celborn, a dragon, Eä, Fëanor, Galadriel, Húrin, Ingwë, Jolly Cotton, the Key of Orthanc, Longbottom Leaf, a Mallorn leaf, and
Narya (the Elven Ring of Fire, I don't remember where it first appeared, probably in the last chapter of The Silmarillion; "Of The Rings of Power and the Third Age", but it's been a while since I read it
)