Continuity mistake: Season 6, Episode 6, Known Unknowns: Right after House has given the speech he and Wilson step outside and House removes his tie. After this his shirt collar changes between almost every shot, from being tucked in his jacket to being on the outside of it.
Deliberate mistake: When a patient who is given CPR is seen in the shot, the person giving the CPR does so with bent arms (the correct way to do it is with straight arms). This is deliberate, as straight-arm CPR puts in an amount of strength that frequently breaks ribs. Many films do CPR with bent arms rather than straight to avoid harming the actor.
Factual error: There are several episodes where doctors continue to defibrillate a patient even after s/he flatlines. A flatline (asystole, where there is no electrical activity in the heart) cannot be corrected by defibrillation, which stops a heart that's in an abnormal rhythm and gives it a chance to start in a normal one (the heart has already stopped when there is a flatline).