One really cool thing I learned was why sunglasses are polarized vertically. Natural sunlight, it turns out, is unpolarized, so why does it matter which direction our sunglasses are polarized? They should reduce the intensity of light the same way at all polarization angles. Well, when light reflects off of a surface at certain angles, it becomes polarized parallel to that surface. Because the sun is above us, its light is incident on a majority of reflective surfaces (water, car hoods, the road, etc...) at pretty near the optimum angle to polarize the sunlight horizontally. Hence, vertically polarized sunglasses will block this reflected light, also known as 'glare'. It's really quite a simple and elegant solution to glare, but people don't usually know about the underlying physics of reflected light.

Edit: Ha, I just realized you were asking more in terms of career. Allow me to answer your actual question: I was a mechanical engineer in school, too, and graduated only a couple years ago. The greatest part about mechanical engineering is how varied the subject matter is. It's incredibly broad, yet you get a good depth of study in all fields, and then you can choose to go even deeper in the ones you really like. I started out with a strong interest in mechanical design, then quickly discovered that I dislike thermodynamics, heat transfer, and stress analysis - which are essentially the core of mechanical engineering, and critical to design of physical parts. But that didn't mean I was shit outta luck, because I also discovered the joys of Controls engineering, which is so different from the core of meche and probably why I like it so much. My advice would be to try and find your own personal niche within mechanical engineering, and there are plenty to choose from.

My experience in the workforce, however, has been less than ideal. The culture at a company is so different from an academic setting. The motivation, the expectations, and the colleagues are completely unlike a research lab setting, or a project team, for example. It's best to enter the workforce with this in mind, and then decide if you like the differences or not. Some people do, but I'm actually considering transitioning out of engineering, and relegating it to a hobby.