A hive tool is essential for working with Langstroth hives. They are used to crack apart frames and pry them up. They are also for scraping excess propolis, pounding/pulling nails, warding off muggers, etc. etc. They are usually made of forged steel, are sometimes chrome-plated, and, if you look hard enough, you can even find ones still made in the U.S. This is the classic hive tool. They usually run from 7-10" long and cost, depending on the vender and quality, from $4-$7. I inspected my first hive with one of these, but I don't have any sentimental attachment to it. In fact, I don't like it. It's said to be good for scraping the bottom board, but I can't speak to that yet. My problem with this type is that it doesn't provide the necessary leverage to pop up frames, so what I would end up doing is crushing the wood of the next frame over.
This one is also called a frame lifter/scraper. And it's well named. It's my favorite so far, for I find it makes the hive inspection much smoother. This type usually costs around $12, but I've seen them from $7-18. Generally about 10.5" long.
This is an Italian hive tool, and like many an Italian thing it does look beautiful. It's 12" long and runs about $13. But I note that it doesn't have that little leverage ledge at the hook end. Not having used it, I can only say it would make a nice gift for a beekeeper who already has a couple of hive tools on hand.