simple marinade for shark kebabs?
i take the following & whiz to a loose paste in a small food processor:
fresh chili pepper
red pepper flakes
amounts can vary to taste (test as you go).
the above has a southeast-asian vibe, but you can swap out the fresh chili/lime/soy for oregano/marjoram/rosemary/salt & have it be more italian, etc...
marinade for a while & then grill. The sugar in small amounts fosters nice browning.