Medical Kits are items that allow the player to recover a small amount of HP. There are several types of Medical Kits for different levels, which give different amounts of HP. Their AP counterparts are the Repair Kits.
Currently in IJJI, there is an antihack system that temporarily disconnects and autobans any player who walks into a stack of more than 32 Med Kits in a single location. This was implemented to counter a hack in which players would be "showered" with Med Kits.