Well, the indirect combat spells (especially those with elemental effects) are beautiful for dealing with drones and unseen enemies.
While they might not be flashy, a lot of the Detection spells can swing a fight, especially things like Combat Sense or Mind Probe (surface thoughts include what they're about to do next, you know), but Analyze Object can make you an instant threat with a weapon you pick up.
Health spells. Oh my, the health spells. Do you know how many beautiful debuffs there are in the health spells? Decrease [Attribute], Decrease Reflexes, Intoxicate, and so on. Dropping someone's Reaction or Agility to 1 turns them from a serious threat to sitting duck. And taking the Samurai's initiative down makes him all the easier to fight.
Illusion spells. Also in the 'king of debuff' category. Orgasm/Orgy, Agony/Mass Agony, Remove Sense, Improved Invisibility, Trid Phantasm. So many options to go with here. Orgy is actually one of my favorite spells for a combat build, because it is a solid debuff with low drain, and it is less likely to have any survivors coming after your head if they are incapacitated to 'gushing'. Remove Sense: How well do you think the enemy will be able to shoot at you if you take away their ability to see? Likewise, how well will they be able to shoot at you if you're invisible? Trid Phantasm is a very powerful spell in the right hands. Being able to create realistic, moving illusions is not something to smirk at. I'll just give two examples. 1) What do you mean, there were eight air elementals that were waiting on call here? 2) Dragon. If you can't think of a way that a dragon suddenly appearing on the battlefield can change the flow, then you need to be playing something other than a mage. Even if they suspect a trick, they are going to react. You just can't ignore a dragon, afterall. Of course, you do it too often, they'll start ignoring it, but that's when you summon a spirit and have it take the shape of a dragon. "Oh, its just another illusion, igno--OH MY GOD THE FIRE IS REAL!"
Manipulation Spells. Ice sheet is always a classic, going back to the days of using Grease in D&D. Slipping and falling on your face tends to make your shots go wild. Wall spells have a natural function of halting the enemy, channeling them into choke points, or setting them up for chunky salsa. [Energy] Aura turns a street samurai with a sword into "OH GOD THE PAIN!" since it increases both damage and gives the -half AP. It also means his attacks count as magical for fighting those with ITNW. Petrify (or the permanent, ice-element version I made, Flashfreeze). You know what a statue is really bad at? Shooting you. You know what a statue is really good at? Being pushed off a building to break on the ground below. Fling, it works on grenades, you know? Poltergeist - Nothing says 'go away' like having a room full of sharp pointies going up in a whirlwind. Mass Animate - Oh god, the rug is trying to hold me down while the chair curb-stomps me! Levitate - It can be cast on enemies, too. What do you think will happen if you whip someone up, say, 30-40 meters, and then stop sustaining the spell?