I threw this marinade together in a major rush the other night and it was unusually and suprisingly good:

(measurements are approximate)

1/2 cup olive oil
1/4 cup cooking sherry
1/4 cup bbq sauce (sweet baby rays)
garlic powder
pepper

I marinated a flank steak in it. But I think that chicken would work well, too. I had actually been planning to mix up a marinade involving red cooking wine but grabbed the cooking sherry by mistake and had to totally improvise. Turns out it was a lucky mistake.

mojo croillo from goya.

Ooh I have a good one.
This is good for about 4 large breasts. Increase quantity as needed.

1 cup ketchup - we use off brand
1/2 cup olive oil
2 table spoons soy sauce
1 table spoon lemon juice

It may sound gross and my husband thought I was nuts but its really good on grilled chicken. Make sure you get most of the marinade off before sticking on grill. The ketchup caramel uses into a tasty sweet/salty crust.

This is by far our favorite - more of a spice rub than a marinade thoug, but so good!

http://www.epicurious.com/recipes/food/views/Peruvian-Grilled-Chicken-239923

This is our go to:
http://www.amazon.com/Lee-Kum-Kee-Chicken-Marinade/dp/B001FB6AI4

You can get it in all the Asian markets, and I think some of the regular groceries carry it as well.

This is our other go to:
http://www.walkerswood.com/product_traditional_jerk_marinade.php

Its *really* spicy though. But awesome. Its the "hurts so good" type. You can get it locally at Home Goods.