Plastic lenss are best and they should be secured tightly. Sports glasses are the best obviously. Hockey masks and such are good for protecting the face. One can search e-bay and second hand stores for motorcross face masks or paint gun face masks. These can be expensive but very useful with a slight modification or two.
Ear plugs are useful.
They are cheap and will offer some protection against concussion grendades and other accoustic attacks. They are light and easy to use. At least one piece of paper should be in your shoe or somewhere ele to avoid being taken if arrested. It sucks not having paper in jail. It is useful for all sorts of things.