On the theme of cheap fun, this Vivitar 28mm f2.8 in TX interchangeable mount also qualifies. Not only does it have very good distortion control, it's also very sharp stopped down a little. There are so many different Vivitar mini-wide (28/35mm) lenses out there that it's dizzying to know them all. The same design of lens could be made by different manufacturers. This particular lens was made by Tokina (37), and is quite well built. You may also find a Tokina branded 28mm f2.8 that may share similar or same design. These are very cheap lenses that can produce quite nice results.
Tower in sunset - NEX-5N & Vivitar TX mount 28mm f2.8