One of the reasons I love Planescape torment so much is the variety of different spells that you can cast, many of which are different/unique compared to other infinity engine games.
Some of my favourites are:
– Luck: Crazily underrated I find. Stacks with itself and can give you +8 to all damage rolls – max damage magic missiles, swarm curse etc ... Good duration too (+5 sec per level)
– Swarm Curse: Great AoE Damage for a second level spell, disrupts enemies' spellcasting
– Missile of Patience: INSANE 1st level spell. iirc it does 15+ damage a click after level 11. Using various items like the tatoo of the magi and karlaacs knife can get you to around 30 casts
– Blacksphere: Great CC and damage
– Enoll Eva's Duplication: Most powerful spell in the game. Cast on Dakkon to turn him in to a meat grinder (zerthimon's focus too) or cast on yourself and double your spell firepower.
– Meteor Storm Bombardment: So cool.
What are yours?