I like using mechanical pencils over pens for everyday notes, although I'm probably in the minority. My goto one is the Uni-ball KuruToga Mechanical Pencil http://amzn.com/B0026ICM1E

There's also a slightly more expensive metal version: http://amzn.com/B004OHNTVC

I have both, but oddly enough I prefer the lighter weight of the cheap plastic one. Just feels more comfortable to write with for me.