Spy vs Spy is kind of an underrated game (if you're playing against another person, that is). You have to take your spy of choice around a building, setting booby traps and searching around to find some spy-related stuff, put the stuff in a briefcase, and then hightail it out of the building.

One of the items you collect is a briefcase to stash your stuff in.

But it has an interesting secondary property. When you pick up the case, you get your health restored. So, after you've been in a fight with the other Spy, you can take the case and hide it inside something

And then get it back out for a quick health refill

Just be careful that you don't stick it behind something that's been booby trapped.