There aren't that many lenses you can buy for under $50, especially those that can take unique pictures. The Sima 100mm f2 soft focus with macro lens is one of those lenses that you literally throw around without worries, because the entire lens is made of plastic, including the lens elements themselves. In fact, though I have not tried it, you can probably put it in the dishwasher and it will probably survive the wash cycle.
If you don't know much about this lens, it's a T-mount lens that will fit ANY camera mount. the lens comes in two parts. You focus by pushing or pulling the front lens barrel until it's in focus, and then you take a picture. Extremely simple, but great deal of fun. The lens comes with f4 and f5.6 (or could be f8) aperture discs that go on the front of the lens.
Sadly, the price of this lens has gone up way too much. It used to be sold for under $20 just a few years ago, but now sellers on eBay want $70 to $80 for one.
Sign of Autumn - NEX-5N & Sima 100mm f2 @ f2. Click for larger.
Rose - NEX-5N & Sima 100mm f2 @ f4. Click for larger.
Sign of Autumn #2 - NEX-5N & Sima 100mm f2 @ f2. Click for larger.