Just a quick note, I was lucky enough to get to work in the Houses of Parliment as a contractor for a few months. They do have bottles of HP sauce on every table in the cafeteria.
I prefer Chef Sauce to HP but I suppose that’s just because it’s what I grew up with.
Oyster sauce is good on burgers, I had a burger last week that was 50/50 beef and lamb with a cucumber mint relish on it that was super tasty:)
Old Bay is good, some cumin rubbed on the burgers before cooking is nice, and don’t forget the old standby, Liptons French Onion soup mix!
Or you could skip the buns and simmer the patties in a egg lemon sauce like the Greeks do. Or make little meatballs, brown them or skewer them and grill them with some turmeric, garlic, and fish sauce, then add them to some simmering coconut milk and Thai curry. Toss in some fresh herbs and serve over rice.
Now that I think about it, grilling little meatballs on skewers is amazingly good, you can add all sorts of stuff to them and the grilling makes them even better, plus you can serve them with rice, potatoes, buns, whatever.
Disclaimer: I have lots of weird condiments so all the above is possible in my kitchen at the moment. The idea is, look at your spices and condiments, thin how you use them for non burger dishes and think of how you can incorporate ground beef into them.
The “I’ve Created A Muenster!” Burger:
Mix 1 lb hamburger with some powdered Knolls Cracked Peppercorn Ranch mix to taste, some bread crumbs, and some salt and pepper.
Saute a crapload of onions in 1/2 a bottle of beer until they carmelize. Grill the burgers, place on bottom half of bun, put the onions on top, cover with several generous slices of Muenster (sp?) cheese, put in the oven until the cheese is well melted, cover with toasted bun top.
Die, go to heaven and leave a stinky, happy corpse. 
Lots of good stuff here. A comment about making the patties: don’t overwork the meat. Lightly shape it into a patty, do NOT press it down on a cutting board or other surface. Overworking the meat makes the burger too dense and dry.
For condiment: Try mayo mixed with chipotle. It gives a great smoky flavor and packs some heat. Or add the chipotle to your barbeque sauce.
I am now drooling.
You probably already ate it, but for next time, how about globs and globs of guacamole? With jalapenos, or maybe pico.
I like eating my burgers on lightly toasted french bread. It’s a more interesting texture than your standard hamburger bun.
Mmmm. I just finished a burger that I topped with a Grilling Blend from Sam’s (I’m a sucker for spice blends) and some provolone. Pretty tasty.
My first favorite burger ever, though, involves lots of black pepper, white pepper, and malt vinegar. Wow.
But I’m a vinegar lover, so vinegar on burgers makes perfect sense to me. 
Best,
karol
Monterey Jack Cheese, sauteed onions and mushrooms, and a liberal helping of Homade or Heinz Chili Sauce over a thin coating of real mayonnaise. Served on an onion roll.
If done over mesquite charcoal, a burger to die for.
If you mix a packet of ranch dressing mix in with the meat, they’ll be yummy. Careful, cause that can make them crumbly; you might want to try a binding agent like an egg to hold everything together.
Furthur & I used to make Heart Attack Specials with the ranch in the burgers and then topping them with shredded cheddar & bacon.
Mrs. Furthur
Not that anyone asked, but I need to disagree with anyone who says to mix things in with the meat.
Or at least if they still want to call it a Hamburger.
Call it American Koftah or a grilled meatloaf or something, but a Hamburger, IMHO, is ground beef, period. Mixing in onions, BBQ-sauce, eggs, whatever, means you don’t trust the meat or your cooking.
I knew a guy who added apples to his burgers.
Anything added to the meat except salt and pepper should be treated VERY suspiciously. If you want onions, grill or caramelize or saute some onions and add them later. If you want ranch dressing, pour it on top of your burger. It doesn’t improve the patty.
Just because BBQ sauce is good and a burger is good doesn’t mean BBQ sauce added to the patty is better, and burgers are such a good consistency (if done right) that adding things throws off the balance.
You gotta trust the meat, man.
Oh, I know what you’re talking about! And if for some reason you left room, I highly recommend the Yummy Yammer Pie. And Jack’s Stack is definitely the king nowadays in KC - they’re just too good for words.
Next time you’re in the city, head down to the farmer’s market and go to Planters. They sell spices in bulk, and have a fantastic blackening mix that’s perfect on grilled chicken and burgers. Plus, don’t forget a bag of chili powder when it’s cold outside - it’s dynomite.