It's a toss-up between these two for my all-time favorite recipe.  The first started out as someone else's recipe, but as usual I made modifications based on our likes/dislikes & what was missing from or in my spice cupboard. 

  The second is from my favorite restaurant on the planet...Boma! 
Spicy-Orange Grilled Shrimp
1 lb shrimp
½ c	lime juice
1 tsp	Tabasco sauce (way too much
probably s/b 1 tsp)
2½ Tbl	balsamic vinegar
1 Tbl	black pepper
1/3 c	orange marmalade
2 Tbl	oil
1 tsp	Kosher salt
2 Tbl	cilantro
1 tsp	orange peel
	garlic, minced (I just use a heaping soup spoon full  we like garlic! 

)
Mix oil, vinegar, & lime juice together in a sauce pan & heat on a medium setting. Add marmalade, Tabasco sauce, salt, & black pepper then mix well. Add cilantro, garlic & orange peel. Remove from heat. (Alternately, don't bother to heat - just whisk it really well before adding cilantro, garlic & peel.)
Arrange shrimp in a deep glass dish, pour marinade mixture over them, cover, refrigerate for 6-24 hrs., then grill on BBQ until done. (Less time is required - maybe 6-8 hrs - if using cooked shrimp.)
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FLANK STEAK MARINADE
from Boma, AKL
Yield:  enough to marinate about 1½ lb steak
¼ c	ginger	
½ Tbl	thyme
2 Tbl	garlic, minced	
¾ tsp	turmeric, ground
2 Tbl	sugar	
¾ tsp	crushed pepper
¾ tsp	cardamom, ground	
¼ c	soy sauce (low sodium is fine)
½ Tbl	coriander, ground	
½ Tbl	Worcestershire sauce
Mix all ingredients in a large bowl.  Add steak and marinate for 24 hours.
[NOTE: This is very thick  more like a paste than a normal marinade.]