I've done a bunch of demos and I just did one all day at Bass Pro yesterday. I did Smithfield marinated pork tenderloins seasoned with my rub, cooked indirect to 145, sliced 1/4" thick, and poured some of my bbq sauce on the cutting board for them to dip in. A big hit, very little prep.
Another great choice is boneless skinless thighs, especially if you have some GrillGrates to use on your Weber. Put the grates right over the coals, season with my rub, and grill them off in about 5 minutes with killer grill marks. Cut them into chunks and dip in my sauce. Cheap, fast, really tasty.