Round robin tournament
The Round-robin is a style of tournament commonly used in the SCA to allow everyone to fight everyone else. The victor is the fighters with the most victories. Finals should only be required if there is a draw. This format appears superficially fair since everybody gets a chance, even the less experienced.
The major disadvantage is the increasing number of bouts as number of contestants rises (3 for 3 fighters, 6 for 4, 10 for 5, 15 for 6, but then 21 for 7, 28 for 8 and 36 for 9) which can make for long sessions. The audience can get bored, if not the combatants. After all, how many times can you watch Squire Should-Have-Lost-Weight having his helm smashed in?. Some fighters may also get tired waiting their turn, especially as time creeps on.
There is also the issue that, in later rounds, cunning tactics come into play, as individual opponents' weaknesses are analysed, and styles and weapons used are varied to take advantage of these.
Sometimes, due to time restrictions or other reasons, an incomplete round-robin is used. This means that the draw is worked out the same way, but the number of rounds are reduced, so the fighters will not be able to fight every other fighter, just a selection of them. However, each fighter should still compete in the same number of bouts.
Another option when you have a large number of fighters is to create pools of no more than five or six. The pools run concurrently with the winner of each pool advancing to the next round.