Most of my favorites are from a shounnen series called
Pandora Hearts, so I'll try to list as many as possible.
Red! Alice x White! Alice Why? Because twincest/selfcest is smexy. There's even a doujinshi by my favorite doujin author for sale!
LinkRed! Alice x Sharon Rainsworth Not only is it cannon (they've kissed, and Sharon has...a weird fetish for lolis like her.... >.>) they go real well together!
Echo x Noise May I say more? GOTS TO LOVE THE SELFCEST! : D
Echo x Red! Alice Since the author seems to love that pairing so much. (they've never even talked to each other but the author has a whole bunch of pictures of them holding hands and in intimate positions.) Plus it is sexy since they're the oldest of the loli characters, so they do have some breasts, but aren't mature enough so that they really know about romance yet.
Charlotte Baskerville (Lottie) x
Ada Vessalius THEY'VE FRENCHED AND GROPED EACH OTHER! (anime version only, in the manga, Lottie just kidnaps Ada and her brother, and pretty much sexually harasses them both) Plus they both have big breasts so it adds to the sex appeal.
And I KNOW
Vocaloid isn't an anime or manga, but I still support yuri pairings for it.
Luka x Miku
Rin x Luka
MEIKO x Rin
Luka x MEIKO
Kaiko (Kaito's genderbend)
x Miku
Rin x Miku
VY1 Mizki (CUL)
x LilyLily x Luka
Miki x Yuki