Well, if we're going to have those types of magical-girl entries, how about Kaitou Saint Tail? (Just be glad I'm not suggesting Tonde Buurin...
Or maybe Moetan.) There's also the Mermaid Melody series, though G-Force 1
already attempted it, somewhat, on fanfiction.net.
(Come to think of it, did anyone actually attempt a Ranma/Shugo Chara crossover?)
And, if we're including Macross 7, how about Macross Frontier?
Hmmm... how about...
Transformers: Masterforce (if I'm remembering the series name correct... the one with Minerva and the other kids who become TF heads.)
Majin Tantei Nogami Neuro
Idolmaster Xenoglossia (I wrote a bit of an idea on this one, myself...)
Getsumen to Heiki Miina
Telepathy Shoujo Ran
Jigoku Sensei Nuube
Asura Cryin (probably misspelled that one)
Still alive, but failing miserably at dodging Real Life.
(Homepage currently down.)