It can be hard to find a great pen that doesn't cost an arm and a leg. The Pilot G2 Pro pen is an excellent pen that is also quite cheap; the last two I purchased were only $3-4 each. There are ink replacements available for the pen that are also very inexpensive.
The Pilot G2 Pro pen has numerous strong points, including a comfortable grip, a simple yet smooth click device, and a large barrel that feels nice in the hand. The pen writes smoothly and accurately and even performs well in weather; I've used the pen to write on a manifest in the rain and the ink still appeared fine.
This is a great pen for anyone that needs a reliable device; I've met police officers and bicycle messengers that swear by the Pilot G2 Pro because it never lets them down.