Trivia: Val Kilmer is widely believed to be the most historically accurate portrayal of Doc Holliday. He is the same height, same build, and uses phrases used by Doc Holliday (eg "I'm your huckleberry" and "You're a daisy if you do").
Factual error: During the gunfight in the lot behind the OK Corral, Tom McLaury is firing a six shooter at Doc just before Doc fires his shotgun in the air to scare Tom's horse away. The mistake is that Tom McLaury wasn't armed during the actual gunfight. He was shot by Doc while he was reaching for the rifle he had stored in his saddle. (01:14:58)
Revealing mistake: When Wyatt and the others leave two cowboys hanging in front of the Dragoon Saloon, you can see that neither man actually has a rope on his neck. As the one man swings around, on his vest you can see the outline of the rope going straight down into the harness that's holding him. (01:25:35)
Continuity mistake: During the fight at the OK corral, Doc Holiday has a double barrel shotgun but he shoots it three times, once in the air to spook the horse, once again to shoot the guy behind the horse, then the scene changes and he shoots another guy with the same gun without reloading.