My built is a metamagic evocation specialist. Hes currently at 13 and game max lvl is 18:
Scribe scroll, spell focus evocatiom, Additional trait (+2 ini, -1 level when using metamagic on fireball), spell penetration, selective spell, intensified spell, dazing spell, quicken spell, greater spell penetration (empower spell and spell perfection fireball at 15 and spell perfection icy prison at 17)
Exploits: Consume magic items, Dimensional slide, counterspell, potent magic, quick study, school understanding (admixture to select spell element), metamagic knowledge, metamixing, greater metamagic knowledge
He's an extremely flexible blaster/controler hybrid with potent blast dmg (high Dc, high vs SR, can select element), added aoe crowd control on blast (dazing), excellent single target control from icy prison and walls.
He can do all that and also keep some utility spell prepared so he really feel like hes always ready for the challenge presented.