The Machine Gun
Human Wizard9/Mystic7
Feats:
Spell Penetration (Human)
Spell Focus - Any (1st)
Quicken Spell (3rd)
Twin Spell (6th)
Greater Spell Penetration (9th)
Scribe Scroll (Wizard bonus feat)
Extend Spell (Wizard5)
Equipment: Lesser Rod of Quickening
Setup: By 7th level, a Mystic can permanently apply the Empower feat (through Spell Secret class ability) a total of 4 times. Drop it all on Magic Missile. Now, Memorize 5 Twinned Magic MIssile, Haste, and Spell Haste (From the Villiagn Design Handbook; 2nd level spell).
Surprise Round: With surprise partial action, cast Haste. With Haste partial action, cast Spell Haste. With Rod of Quickening, cast Quickened Twinned Quadruple Empowered Magic Missile.
Round 1: Cast Twinned Quadruple Empowered Magic Missile as a standard action. Cast Twinned Quadruple Empowered Magic Missile as a move-equivalent action (from Spell Haste). Cast Twinned Quadruple Empowered Magic Missile with partial action from Haste. Cast Quickened Twinned Quadruple Empowered Magic Missile with Rod of Quickening.
Damage per missile: (3.5 *3=10.5)
As a 9th level caster, each Magic Missile spell produces 5 missiles, doubled for being twinned. That's 10 Magic Missiles per spell.
Surprise Round: 10 Magic Missiles (10*10.5=105)
Round 1: 40 Magic Missiles (40*10.5=420)
Total Damage: 525
Since Spell Haste doesn't grant any additional actions, it stacks with Haste (It allows 1 spell per round to be cast as a MEA). Even without Spell Haste, you only lose 1 casting, or 10 missiles. The smackdown still does 420 points of damage.
The Mystic PrC, which this class is built around, was designed before adding +1 caster level became standard practice. If we were to assume that the Mystic PrC was actually a +1 caster level/2 levels class, and you went wizard7/Mystic9, all of the magic missiles would be empowered 1 additional time, as well as maximized for free. If you add the Persistent power feat, you can cast a Persitent Spell Haste at the beginning of each day, which allows you to eek out 1 more swarm of Magic Missiles. Also, you could Empower each Magic missile Spell cast 1 additional time. So, you would be casting Twinned Maximized Septuple-Empowered Magic Missiles.
Damage per Missile: (5*4.5=22.5)
Surprise Round: 20 Missiles (20*22.5=450)
Round 1 : 40 MIssiles (40*22.5=900)
Total Damage: 1350.
Just imagine what this guy could do if he chose to modify Ray of Enfeeblement instead (155 strength damage anyone?).