I have done "little Smokies" in BBQ sauce, it was for a bunch of teenagers so I was afraid they would be too messy but worked out fine. We have done the Taquitos - pizza roll things, like the bagel bites. Check out Costco, they have so many appetizer type foods in their frozen food section.
One thing I do make from scratch is twice bake potatoes - we call them Western Potatoes. Where you bake the potatoes, then cut in half, scrape out the inside, then blend in butter, cheddar cheese, chives, salt and pepper to taste. Then spoon it back into the potato skins, cover with cheese and bake at 350 degrees until the cheese is melted and heated thru - about 25 - 30 minutes. When I do it for a large group I look for the small potatoes.