i LOVE the performer gas assist
As for me, the
thermapen (or actually, all thermometers in general).
I was such a grill snob, i refused to use any thermometer and insisted that a good chef should be able to know when food is done.
I spent years gauging the time, temps, and doneness of meats using my hands, fingers, and occasionally a fork, knife, or toothpick.
Eventually I realized that having the thermapen is a HUUUGE advantage. HUGE. I don't think I could live without mine.