I can't be the first one to think of this, but thought I'd share anyway. A few days before brewing I put a gallon jug of Arrowhead in the freezer. When it came time to cool my wort, I sat the jug in a pot of warm IO Star solution to unstick the ice from the jug, then cut the jug away from the ice with sanitized scissors. In went the ice into the wort, I sat and stirred it a bit, and within maybe 15 minutes the ice was melted and my wort was down below 90°.
Combine wort with water in carboy up to 5 gal and I was ready to pitch. No wasted water, no time spent crouched over ice-filled bathtub, no immersion chiller necessary. Worked incredibly well.