Sequencers and the like.

[Mitro Jellywadder]

What make the sequencers and contingencies the best are the (almost) zero casting time. Once an enemy shows up, click the sequencer and it's off. It's kind of a sneak attack. You always get the first lick in. Contingencies are the same, except you don't have to do anything. Whether they're saving your butt (mirror image, stoneskin, etc) or inflicting mass damage (abi's..death..cone of cold..etc)

With the contingencies you can set it to save your butt (instead of *pause* click the potion..hope I drink it before I get hit again) once you drop below a certain hit point level you will automatically cast defensive spells with a contingency.

Spell sequencers are just *free* massive killing and/or defensive spells. You can store the sequencers, rest, and then you still have your full casting power, plus the sequencers stored.
It makes killing monsters that much more fun.