Most Fighting-types are Physical attackers (not so much as Special attackers). But, only a handful of Fighting-types can learn Focus Blast as a TM. Here is a list all the Fighting-types that can learn it through TM:
Mankey / Primeape, Poliwrath, Machop line, Hitmonlee, Hitmonchan, Heracross, Combusken / Blaziken, Breloom, Makuhita / Hariyama, Meditite / Medicham, Monferno / Infernape, Riolu / Lucario, Croagunk / Toxicroak, Gallade, Pignite / Emboar, Timburr line, Throh, Sawk, Scraggy / Scrafty, Mienfoo / Mienshao, The Swords of Justice (Cobalion, Terrakion, Virizion, and Keldeo), Chesnaught, Pangoro, Hawlucha, Crabrawler / Crabominable, Stufful / Bewear, Passimian, Hakamo-o / Kommo-o, Pheromosa, and Marshadow
"Focus Blast is the only special Fighting-type move that has an accuracy lower than 100%." So, Focus Blast wouldn't be a worthwhile move to teach your Fighting-types.