As a wizard myself, I've been through a little, and learned a lot of what's useful.
Slow - Got a 100 armed enemy you have to fight? Their 100 attacks are now just one, and they can either move or attack, and they are at -1 to their one attack, and -1 to Reflex saves. (Just make sure they can't pounce you)
Blindness/Deafness - Got a ranged character you're fighting? Permanently disable them with this spell. Harpies? Give your fighter immunity to their Harpy song.
Communal Resist Energy - Wow, this is a good spell. Fighting something with an area of effect? Make them cry as you become resistant to their energy type. Those dragons didn't know what was coming.
Haste - Want to deal damage? One of the best damage dealing spells there is.
Emergency Force Sphere - About to die? Stop it entirely.
Wall of Ice/Stone - Got tons of enemies? Separate them and fight two easier battles.
Silent Image - Why not make a "Wall of Stone" or "Create Pit" at level 1? "Obscuring Mist" made with silent image causes all sorts of chaos, although this spell really it can depend on your GM.
Dimension Door - Get out of jail free....or....Bring your fighter with you to the enemy wizard.
Fickle Winds (Wind Wall) - Archers? Swarms? No problem!
See Invisibility - When paired with glitterdust, this little gem can foil anything invisible. It's just so obvious!
Ear piercing scream - It's magic missile with a save for half (...basically). If they fail, they are also dazed for one round. Amazing!
Magic Missile - I hit you (unless you have shield).
Feather Fall - I didn't die from that fall, really!
Liberating Command - You're free! With grease, you're even more free!