Sugar. It's the most under-utilized seasoning agent in any cook's pantry. I think it's because we've been so conditioned in the USA to think that sugar == sweet == dessert that we don't even think of the possibilities of using it in savory dishes.

Soup? I use it all of the time.
Sauce? Just today I used it to balance out a slightly acidic pasta sauce.
Meat? Sure. If you want some extra special caramelization, sugar is the way to go. Try dusting your scallops with sugar the next time you saute a batch.
Veg? Any tomato dish that has tomatoes that are slightly out of season would benefit from sugar.

The list goes on and on.

In the past six months I've gotten more and more used to the idea that sugar is an essential seasoning agent along with salt, acids, spices and bittering agents (careful! a little bitterness goes a long way). In the back of the house we doctor things up all of the time to make them taste better and I guarantee you that one of those things that you would never guess that we add is sugar.

Try it the next time you have something that is missing a certain roundness that salt, acid or spice can't bring it. You'll be surprised.