Grill (mine's a beat-up Weber I rescued from my neighbor's curb five years ago)
A couple of mixing bowls (including that chipped ceramic one I refuse to throw away because it was my mom's)
A decent knife (life's too short for dull knives, trust me)
Cutting board (mine has battle scars from years of enthusiastic chopping)
Tongs (the longer the better—I still have a scorch mark on my forearm from learning this lesson)
Whisk (or a fork if you're in my old college apartment where whisks were fancy kitchen tools we didn't own)
Measuring spoons and cups (though between us, I eyeball most of this now)
Your favorite serving dish (I use my grandmother's platter that only comes out for special occasions, because dammit, grilled vegetables ARE a special occasion)