Others
Other sport rules, including versions allowing full contact bare knuckle strikes to the unprotected head, exists, but tend to be small and obscure compared to the above listed major formats. These rules tend to be restricted to a single small style organization or even individual sport event promotions.
Examples of minor full contact rules system are the Shinken shobu rules of Kyokushin-kan, Irikumi Go as used by some Gōjū-ryū organizations (most notably the International Okinawan Gōjū-ryū Karate-dō Federation and the Jundokan Goju-Ryu organization), and the rules of Mumonkai Karate. Kyokushinkan shinken shobu uses a variation of knockdown karate using thin gloves, and allows headpunches, clinching and throws. Irikumi Go is a traditional continuous fighting using full contact, gloves and facepunches, used in Gojuryu karate. Mumonkai use rules similar to knockdown karate, but modified to allow headpunches with protective headgear and thin gloves.
A example of full contact karate rules unique to a single promotion is the Chaos Madmax special event in Japan, arranged by the FSA Kenshinkan style organization. Here fighters fight without gloves or protective equipment, and headpunches allowed.
Read more about this topic: Full Contact Karate, Different Formats