Grenadier said:Humorous answers:
A shinai to create loud noises, so that misbehaving students can be brought in line.
A bottle of bourbon, whisky, or scotch, for medicinal purposes only.
Massage table, and someone at least proficient in the art. Furthermore, the one proficient in the art has to be someone that everyone can trust, since it's not unusual to run into people who are afraid of other people's hands on their bodies.
Training can be tough on the muscles, and even the toughest can get cramps, pinched nerves, etc. This is even more true in Jiu-Jitsu, when people will sometimes fall incorrectly (it happens to everyone at least once).
A session of massage therapy can dramatically cut down on the intensity of the pain, as well as the length of suffering. Having various heating and cooling linaments are invaluable as well.