My burgers always get Dijon mustard and either guac or pesto. Ketchup once
in a while. I mayo'd one burger and it was bland, no zing. Since my burgers
are breakfast, I only garlic and onion powder them if I don't have to run
errands. I once got hit by powerful garlic breath from a Home Depot
employee. I actually stepped back!

When I had free-range buffalo I didn't put anything on them, not even
cheese. The delicious meat flavor stood alone. Cooked to bloody rare.

Andy