A collection of various funny/interesting things I've discovered throughout the years playing Assassins Creed 1.
Silent but Deadly
Leaning against a chest right behind this Templar in Damascus and you can gentle push him without performing the animation. Add some fart sound effects and it creates a funny scenario.
Glitched Spot
In Damascus there is a sequence of freerun beams that will leave Altair landing on midair at the end, if he stays close enough to the wall.
Benchwarmer
You can get on a bench right when a guard has detected you. This leaves you in the anonymous state.
Moonwalk
This was difficult to pull off. What you want to do is kill an enemy by a posted guard, then get shoved by him when he is about to investigate the body. This can cause a backwards walking effect, aka Micheal Jackson Moonwalk.
Walking on Interrogation Target's Head
Do I really need to explain this one?
Majd Addin's Room
If you reload the checkpoint during or right after Majd Addin's assassination, a guard is spawned inside the building Majd comes out of. To get in there get the guard's attention by attacking him and hope he hits back, allowing you to counter your way in.
Guard Room at Funeral
When more guards are summoned during the funeral, they appear from inside a building. Turns out you can walk in there when the doors are opened. While you are in there, high level guards can combo attack their way in; you can use that to counter your way out.
Desynchronized Scene
This is based off a previous exploit, caused by fast traveling out of the area during an assassination, then returning and restarting the mission.
http://thehiddenblade.com/majd-addin-quits-his-job
Upon revisiting this, I found you can get through all the Majd Addin post scene dialogue by standing in a sweet spot. If you start the scene right after the last kill the game will desynch you during the scene.