which burner do you use?Surprised no one said it yet, but my AG equipment! I've had so much more fun brewing since I upgraded.
If that doesnt count I'd have to say a more efficient propane burner. Brings wort to a boil in half the time using roughly the same amount of gas. Love it.
This. I've got a fancy automated electric AG system, stir plate, and kegging system but this is what netted the single best improvement in the quality of my beers. The others were great, but this is where the money should go first - thus being my favorite.Temp controlled fermentation chamber.