One of the handiest freezer stock foods is frozen peeled shrimp. They aren’t as tasty as unpeeled, unfrozen shrimp, but they sure are handy to use. I almost always have a bag or two around.
Here are two recipes with a little kick to them that can be made in just a few minutes from frozen; both are perfect for bento.

This is a real cheater’s version of shrimp with chili sauce. It’s cooked in about 5-6 minutes.
For one bento:
Put the frozen shrimp in one layer in a small frying pan. Sprinkle with salt and sake. Heat up the pan with a lid on, and let steam-cook for about 2 minutes. Turn over and cook another minute or so until cooked through. Add ketchup and chili paste, and mix. Let cool before packing into bento box. Optionally sprinkle with a little chopped green onion.

Frozen shrimp are combined with wacked up green onion, and pan-fried or deep fried. Here I’ve pan-fried them. The furikake adds flavor and a nice crunch. To ensure the fritters don’t turn greasy when cooled, be sure to drain off the oil very well.
For one bento (make 3-4 little fritters):
Roughly chop up the frozen shrimp into small pieces (you could also use tiny frozen shrimp here). Combine with the green onion, salt, paprika and furikake. Add the flour and cornstarch and add just a little water so that everything is coated.
Heat up some oil in a frying pan. Drop the fritter mixture into the hot oil with a tablespoon. Shallow fry or deep fry the fritters until crispy on both sides. Drain very well. Cool before putting into your bento box.
Make-ahead note: You can make these fritters in advance and refrigerate (up to a day) or freeze (up to a couple of weeks) them. Heat and crisp them up in a toaster oven before putting into your bento.
Links:
[1] http://www.justhungry.com/the-role-alcohol-onion-and-ginger-japanese-meat-dishes
[2] http://justbento.com/handbook/johbisai/homemade-furikake-no-3-noritama