If I were going to give an award to a vegetable for being fast and easy, it would probably go to radishes. These spicy and beautiful vegetables grow incredibly quickly from seed. They don't grow very deep, so you can grow them in a relatively shallow container (4 inches deep is the minimum for most radishes).
There are many different kinds of radishes, that come in all kinds of colors and shapes. The ones pictured here are a French breakfast radishes.
I like planting my radish seeds thickly, because I love eating the young radish greens, after I thin them. In fact I like the greens even better than the radishes because if eaten when young (less than an inch to an inch and a half tall), the radish greens can be tasty with just a little bit of the spice that full grown radishes have. You can eat radish greens when they get older, but they can be spiny and have to be cooked to lose the prickles.
Most radishes are a cool weather vegetable, so plant them in early spring. Plant radishes in a good, fast draining potting soil in a container with good drainage. Sow the seeds about a half inch deep (or follow directions printed on the seed packet) and place in full sun to part shade. Keep soil moist. Radishes germinate at lightning speed - sometimes in just a couple of days.
Harvest your radishes when you can see a good sized top poking up out of the soil. Grip them at the base of the stem and slowly pull them out of the soil. To keep radishes fresh, remove the tops right after you pick them, then refrigerate.