I made some burgers tonight that were fantastic. This isn't exactly an innovative recipe, but it's so damn good, and pretty easy.

First get ground beef that is 15 to 20% fat. If you want to eat health food, eat something else. Add to the raw meat-

Salt and fresh ground black pepper.
Chopped sweet onion. I had 1.5 pounds of meat, so I used half a large onion. Chop it as fine as possible. I have a slap-chop type thing that turns it almost to mush, but not quite. You just don't want big crunchy chunks.
Chopped roasted garlic. I used a heaping teaspoon. I like the stuff from the jar because it has a more mellow roasted flavor, and it's cheap and convenient.
Panko breadcrumbs. I used between a quarter and a half cup. You don't want the burgers to taste bread-y. The point is to hold in the juices and fat.

I love grilling, but I've been using my broiler more than my grill lately. It's so much easier to get things to cook evenly, and with a lot less char.

If you like onions as much as I do, top with sliced raw onions and some iceberg lettuce for a nice crisp cold contrast- like a McDLT.