Or, in the parlance of the construction industry - a gun.
One of the most commonly used tools in what I do, yet one of the most commonly overlooked.
Starting from the ground up - the battery. The battery is what makes this tool even possible. And the advancements in them have simply continued to move forward. From NiCd to LiIon, 12 to 14.4 to 18, 19.2, and 20v systems. The life improves pretty constantly, the power too. And the portability is without question a huge selling point - before this, it was no big deal to keep a long cord with us to make things happen. However, now it is only necessary to have a charged battery.
Coming up the grip - corded drills were, and still are, kind of bulky - not very comfortable to hold. But, with the advent of the cordless drill, ergonomics were suddenly in the picture. And, oddly enough, once cordless drills began to look at ergonomics, comfort, and ease of use, so did other tools. Suddenly hammers were made to fit your hand rather than being big and slick (a much safer option, I feel...)
Next is the trigger. Named as such for the gun like stance the drill takes. Some of the larger, bulkier corded drills were hard to pull the trigger, but with the cordless options, it is a much easier design to use. They are also smaller, now occupying the real estate of one finger rather than the previous 2, or more aggravating 1.5.
Beyond that, much of the drill is unchanged. But, the revolution that happened from the trigger is enough to have revolutionized much of the construction industry for the better.