I'm a wet shaver, so I tend to go overboard with my shaving kit. I use a folding brush, one of the little Gillette razors (kind of like this), plus a few assorted soaps and creams. Despite being rather over the top, the entire kit comes in a tad under 8 ounces.

Of course, if it's just a short tour, or I'm not going to really by interacting with people, I'll just let it grow.