I'm a gas grill guy too. I grill 12 months a year, at least once per week even with 12' of snow.
For my typical burgers, I add garlic powder, minced onion and some black pepper to the meat, mix it, patty it, and grill it. It's not fancy, but it's tasty.
For chicken It all depends. I just tried the Sweet Baby Ray's marinade and it's pretty decent. I've also done the minced garlic, teriyaki and soy sauce route with much success.
Try everything once is my opinion.