Friendly fire

It may happen in many ways. By accident, as part of a plan (i.e. undercover situation), or when there's some tension/misunderstanding between friends and escalates until someone gets hurt.

"Possession" and "mind control" are possible situations too.

Check the complete Tropes index for more.

Animes
Ao no Exorcist


 * 1x18: Possessed Konekomaru (post-discovering Rin's secret) attackes and beats up Okumura Rin. There's the classic "grabbing his head with my big hand" moment too.
 * 1x24: When Rin's voice finally manages to wake up his possessed brother's consciouness, only part of Yukio's body was under his control, and Rin ends up shot.

TV Shows
Arrow


 * 1x22: Oliver (Stephen Amell) and his mother are "kidnapped" by the vigilant (actually Diggle), to make Moira confess the true about the undertaking. Oliver gets punched many times, which leaves his face with a few bruises, beside a limping (although for a short time).

Lucifer


 * 1x04: Chloe shots (more like a graze) Lucifer (Tom Ellis) on the leg, kinda considering the possibility of him being the actual Devil.

The Man in the High Castle


 * 1x03: Frank Frink (Rupert Evans) plans to kill a public figure for vengeance, and when his friend - DJ - finds this out, he tries to stop him. He takes Frank's gun and threatens him with it so he wouldn't leave the house, but when Frank tries to take it back, DJ accidentally shots him on the arm

Walker


 * 1x11: Cordell Walker (Jared Padalecki) gets shot on the arm by his daughter, who was hiding, scared, and only saw his gun hand before shooting.

Movies
Lord of the Rings 3: The Return of the King (2003)


 * Thinking that Faramir (David Wenham) is dead and ignoring when told otherwise, Denethor is determined to burn him.

Pirates of the Caribbean 2: Dead Man's Chest (2006)


 * Will Turner (Orlando Bloom), because of a mistake made during labor at Dave Jones's ship, is taken to be punished, and it's his father who (voluntarily) holds the whip.

Walking Out (2017)


 * During an encounter with a bear, David - the son - is up on a tree and Cal (Matt Bomer) - the father - is on ground level, trying to get the animal away from his son. David tries to help shooting the bear, but the bullet hits Cal's leg instead. He can't walk for the rest of the movie.

Dramas
The Untamed


 * Ep 16: Wei Wu Xian (Xiao Zhan) tries to stop Jiang Cheng from going back to their clan and seek revenge against the enemies who destroyed it. Jiang Cheng becomes violent against him, choking him on the ground and yelling all the reasons that was his fault.