A wand of spectral hand is a must for any cleric/wizard type. Ranged healing spells are very useful.
A villain in the campaign I ran used blindness and feeblemind, both with the Chain Spell metamagic feat. Those two spells disabled half the party.
Ages ago, in 1E days, my friend Dan's wizard used transmute rock to mud on the stone floor of a room across which were trudging two iron golems. The golems sunk into the floor and out of the combat.
Later, when I was running a wizard, I used a variation of the same trick: stone to flesh in the path of advancing oozes. They ate the floor; the party escaped.
A fight aboard a pirate ship while I was running a cleric. My cleric turned to the foolish orc fighter in heavy armor and tossed out a command to swim.
In a high-level 2E campaign, I was running an uber-druid. In an area where magical effects were amplified to dangerous levels (i.e., fireballs exploded in 80-foot-radii, et cetera), the GM was certain we were hamstrung, unable to safely use our characters' magic, as the horde of ogre fighters rushed our position. My druid tossed down a june bug, retreated, and hit it with giant insect. The june bug grew so large it clogged the corridor, creating a wall of bug between the party and the advancing bad guys.