A lot of photographers I follow seem to like the 50mm prime least of all the lenses they've used, but I still can't figure out why. I love it for a number of reasons... not the least of which is the price tag. Plus, it's not called the nifty fifty for nothing. ;) So here are my thoughts on why this little guy deserves to be in your bag (or better yet, on your camera)... and some fun examples of what you can do with it!
1) Spare Your Wallet
Being one of the cheapest (only in terms of price) lenses on the market, it's a far better lens to start with than most kit lenses. In fact I don't know why camera manufacturers don't just offer it as a bundled item instead of the 18-55 for example. You may not have as much flexibility with a prime as you would with a zoom, but odds are you'll get better (and more creative) images due to greater control over aperture. The 50mm also teaches you to "see" better in my opinion, because it forces you to move your feet for the composition you want.
2) Get in Close
If you like macro photography and you're interested in playing with it... you don't need a special lens to get started. The 50mm has a minimum focusing distance of about 1.5 feet, so it performs quite well for close-ups of flowers, bugs, still-life... whatever you're into. You won't even have to worry much about lens distortion, which can sometimes be an issue for zooms with similar focal ranges (like the 24-70mm). For extreme macros, you can also buy an extension tube kit or a reverse mount adapter on Amazon, allowing even more creative options.
3) Create Beautiful Bokeh
I'm not sure about other manufacturers, but Nikon's lineup includes an f/1.8 and an f/1.4 version of the 50mm. I own the f/1.8 which is less expensive, but can still create some pretty dreamy bokeh effects. In some cases you can blow out the background entirely depending on where your subject is in relation to it.
4) Shoot in Low Light
Your camera's sensor has a lot to do with how well it can deal with dim lighting of course, but because the 50mm is so fast, it does extremely well in low light situations... without having to add a flash or bump your ISO to unearthly heights.
5) Be Stealthy
If you're into street photography, it's easier to blend in with smaller prime lenses like the 35mm and 50mm. There is an unfortunate stigma associated with long lenses. People equate them with stalker-like behavior, which can immediately make them feel guarded and distrustful. Even if you're shooting a planned session with a client, sometimes large lenses can intimidate young subjects. A 50mm can help to alleviate suspicion and set your subjects more at ease.
6) Aim One-handed!
Controlling camera shake can be troublesome with heavy lenses and tripods aren't always ideal. A light weight lens gives you the ability to move around quickly and frees up your stabilizing hand to instead hold a reflector, off camera flash or... I don't know... a garden hose to soak your kids with on a hot summer day.
7) You Can Pack Light
I've heard over and over what an awesome lens the 35mm prime is. Photogs who have one seem to adore it. Since I don't own one (yet), I resort to the 50mm when I don't feel like lugging around heavy gear. The sunset below was captured while heading to Fort Collins for dinner one night. The only thing I was in the mood to lift was a stout margarita, so I put on the 50mm and off we went. No one wanted to stop so I could get a better shot (we were all starved), but I would've missed the chance entirely if I hadn't had a small lens to bring along.
8) Let Your Kids Have a Go
I mentioned earlier that the 50mm is a good starter lens for someone new to photography, and that holds true for kids as well! If you have school age children (or teens) who are interested in what you do, hand it over and encourage them to shoot. You might be surprised by what they come up with!
Last April I took my kids to Denver for a Clickin Moms Photo Walk and let them take turns with my old D90. I had the 50mm mounted and turned them loose with the camera set to Aperture mode. Later that day as I was importing all our shots, I noticed they got some... interesting compositions. And even though we all walked the same path, they saw things I totally missed! It was a great way to connect with them and we all had a fun time shooting together.
9) Get Creative!
One of my son's favorite photos to this day is from a little project we did a few years ago involving some Star Wars action figures. We tried to recreate the scene from The Empire Strikes Back where Vader corners Luke on a walkway and tries to convince him to join the Dark Side. (Oh the drama!) As you can see, we shot the concept on a windowsill. Due to the constraints of my son's room, I only had one angle and had to get in tight. I had the 50mm on my D90 (which essentially turned it into a 75mm with the crop factor), and thanks to the short focusing distance, we got a fun shot.
Want to see more? There are a ton of awesome 50mm images on 500px!