However, these pencils do have their drawbacks, the most annoying one being they sometimes jam. But this metric is good for classifying these pencils by jam frequency and ease of unjamming.

Some great features of mechanical pencils are:

On the lower end, I highly recommend the Pentel P205 0.5mm. At about $4.30 US per pencil, it hurts a bit to lose it, but it is the only pencil I've used that is easy to unjam if it gets jammed. The eraser is small, good for detailed erasing, and the shaft is very strong (no bending these in half with one hand while bored).