Their own casting.

[Ryu_Bonkosi]

I was just wondering what classes are there other then Ur-Priest, Sublime Chord, and Blighter that give 9th level casting in 10 levels.

[arguskos]

Apostle of Peace (BoED) does it. Divine Crusader (C. Divine) does as well, kinda.

I think there's a few other, more obscure, ones.

[Thrice Dead Cat]

There's also Beholder Mage.

[Kalaska'Agathas]

And Shadow Templar, if you're allowing Dark Sun 3.5 material (which is a fan-project).

[Divide by Zero]

Illithid Savant can get it in three levels if you somehow manage to get a hold of a level 17+ caster's brain.

[Alleran]

Illithid Savant can get it in three levels if you somehow manage to get a hold of a level 17+ caster's brain.
If you can absorb special qualities, then just gate in an Ethergaunt, a Planetar or a Solar.

[Dusk Eclipse]

Here ya go (A handy list) (http://www.giantitp.com/forums/showthread.php?t=181091)