I'm starting this thread to see if there are some interesting things you can do with PrCs that aren't usually considered the cream of the crop.
For example, Eldritch Theurge can be used to stack spells, due to the fact that Spellblast turns an AoE spell into an Eldritch Essence of at least 4th level. And then they get Eldritch Spellweave, which lets them throw it onto any targetted spell.
Combine with a Spellwarp Sniper for win.
So, do you have any interesting combos?