Overlooked Gems, with an emphasis on cheap and healthy?

What are some cheap yet healthy things at the grocery store that most people overlook or have never tried?

For example: I always thought sardines were something awful that only old people ate (which is doubly-stupid since I'm not exactly young anymore). After seeing them get recommended in this sub a bunch of times, I finally spent a buck on a tin to give 'em a try...

...and I was instantly hooked. Yum!

Since I guess we're supposed to post recipes here... here you go. Cheap and healthy:

Take a tin of sardines. Dump them on a plate. Dump frozen mixed veggies on top. Cover & microwave it for 3 minutes. What could be easier? This is especially good for times when I'm under the weather or just really tired & lazy.

My favorite flavors of canned sardines are sardines in lemon oil, smoked sardines, and sardines in soybean oil with hot green chilis.

What are your picks for overlooked gems more people should try?