There's lots of ways you could make him, though I'm guessing that a Barbarian 5 / Fighter 4 / Sorcerer 1 / Dragon Disciple 10 would have a nasty set of offensive (as well as defensive) tricks.
Off the top of my head I like any of the following:
Bbn4 / Sor1
Good Stuff: Rage (2/day), fast movement, uncanny dodge, good skill points / selection.
Bbn2 / Ftr2 / Sor1
Good Stuff: 2 bonus feats, Rage (1/day), fast movement, uncanny dodge, better than fighter skill points / selection.
Ftr4 / Sor 1
Good Stuff: 3 bonus feats, access to weapon specialization.
Pal2 / Ftr2 / Sor1 (fun with gold/silver dragons)
Good Stuff: 2 bonus feats, detect evil at will, smite evil (1/day), immunity to disease and fear, and charisma bonus to saves (basically a +2 or more to all saves, since you're most likely to have at least a 12 charisma, and you gain +2 to charisma later on in the prestige class).