Games where you can use both spells and guns.

Silverfall. Older, but it's on Steam.

magicka ftw

Hellgate London?!

Risen 1, they remove spells in Dark Waters

That's an awfully loose criteria. A huge slice of JRPGs would be what you're looking for.

Shadowrun returns :)

There's also Risen 2 which has guns, swords and voodoo, but that works a bit different than the usual videogame magic.

Penny Arcades on the Rain-Slick Precipice of Darkness

Fable has magic and guns. Saints Row IV has super powers, GTA IV has some magic mods, and here are some guns in Skyrim

Oh and Shadowman is guns and voodoo magic and it's pretty hard as well :)

Septerra core has guns and magic too, Might & Magic and Wizardry are scifi games cleverly disguised as elfdwarf fantasy :) so they actually have guns too.

Then there's Anachronox which is guns and "magic" if you count stuff like mass effect's biotics as magic.

Dungeon siege 3 has a playable gunslinger character and i guess that the new Van helsing game is something similar although i haven't played that one yet.

System shock 2 has guns and psionic "magic".

Omikron: The nomad soul has a magic element to the story and its setting but the magic there is only used to perform certain rituals so no fireball throwing.

Darkness 2 is pretty much guns and demon magic.

Fable 3 is guns and magic and it's a great game!

terraria.

Magicka. especially Vietnam dlc

Hellgate London!

Magicka with Vietnam DLC.