Grilled portabella caps? I like to marinate them in italian dressing and then stuff them with feta.
Skewers with grilled seiten and red peppers, onions, mushrooms, grape tomato?
I am not huge on veggie burgers, but I do like these soy free sausages -> http://www.fieldroast.com/products.htm
I like the apple/sage one.
oh, you can also make pizza on the grill. Use a whole wheat pita, add some feta (or tofu), tomato sauce, yellow pepper, olives. yuuuuum.
Have you tried grilling tofu? It's pretty good. Just marinate it in italian dressing or bbq sauce and slap a slice right on the grill.