I'd LOVE to see Oh My Goddess items on Gaia. I even designed a dress for their contest at one point that was styled similar to something one of the goddesses would wear for one of the contests because I wanted to wear something similar.
And since FUNimation has the license to it (I'm pretty sure only FUNimation does sponsorships), I don't see it being outside the realm of possibility. But even if they can't get a sponsorship, knock-off items would be nice, too.
Other than Oh My Goddess, I'd like to see Black Butler, Fairy Tail, Rosario + Vampire, Slayers, Negima, Pretear, Sakura Wars, Karin(I think they own distribution rights to it), Rozen Maiden (Again, I think they own its distribution rights now), and Tenchi Muyo items.
It's too bad it would have to be FUNimation series if was a sponsorship, though. I would love to see .hack//SIGN, Fushigi Yuugi, El Hazard, Pandora Hearts, Escaflowne, Record of Lodoss War, or Mythical Detective Loki Ragnarok items. *crosses fingers and hopes for knockoff items from these series*