I bought some chalk pens a few months back so I could write/draw on the kegerator (freezer front is painted chalkboard black). The pens came with some chalkboard labels that are the SHIZNIT for labelling kegs; easy to clean off, and unless they get too wet, easy to read. Chalk pens are also great for writing on glass, so I can label my yeast slurry jars to know what's in them, when I remember to do so; today brewed up an American Strong ale that needed some Notty slurry. Had two jars in the fridge that I did not label (don't drink and keg, kids), fortunately the notty was slightly green from the hops in the last beer it was on.