For the setup before this watch the original video. It demonstrated how to disarm Rodrigo of the papal staff.
After disarming Rodrigo keep the heavy weapon and staff where you can use them again. Take down the target's health as usual, and after the scene open the trapdoor to the vault. Now go back and get a guard to fight you (if you start from any checkpoint after opening the door into the building the guards won't appear in that area). Disarm the guard to make him pick up the heavy weapon, and pick up the staff right afterward.
Fighting Rodrigo with a Weapon
Now here is where the fun begins. Get the guard close to the edge of the pit. During the following scene with Rodrigo you can briefly see the guard. When the fight begins get where the guard will see you. Now here's a glitch in the combat system: Heavy weapons can be disarmed when you only have the option to counter with fists. This was originally discovered in this video.
After Rodrigo gets to one block of health it won't go down lower than that.
Like the title says, a shortcut for silently killing all the guards in the Sistine chapel. Here's the original video.
The only weapon you need equipped for this is poison. I start with the brute at the upper left of the room. Blend-walk out of a group to poison the brute without getting detected (stick by the wall to avoid getting seen by the other brutes). Now walk along the wall and poison the other brutes on that side of the room from behind. After that walk straight across to the other side of the room. The brutes there will see you until you blend back into a group. Blend-walk out of that group and repeat the process. The last brute is blocked off by a structure, so I run to poison him. You can expect for him to exclaim from seeing you, but usually he's poisoned when you're still anonymous.
Now for "killing" Rodrigo. Here's a way to "kill" him with one of the brutes' weapons. This will cause a glitch (not shown in video) with the scene after the memory corridor scene. This glitch was shown before in a video.
However it was done with a heavy weapon outside of the Chapel. It was originally thought you couldn't kill him with a weapon in the chapel. This is because you have to jump from the high place and immediately attack. Running at him with the weapon and attacking will result in desynchronizing during the kill animation. So here's what to do: At the place shown in the video do a wall run and grasp the structure. There's a good chance the weapon will get stuck in the structure. Now climb on the ledge at the place shown, which will have Ezio in a standing positon. From there you can pick up the heavy weapon (make sure you're past the corner of the structure or Ezio will grasp the structure when you press the ). Now you can make your way to the high place without having to drop the weapon. You can probably also use this method to bring the papal staff out of the Sistine Chapel.
This video is based on the clever strategy by KaiyuiKurosaki to disarm Rodrigo Borgia by using the smash attack.
Stabguy illustrates this strategy in a video:
This video is based entirely on KaiyuiKurosaki's earlier story How to Wield the Papal Staff Against Rodrigo Borgia. The idea is to use the Smash attack with a Heavy Weapon to knock the Staff out of Borgia's hands. Before we get to that, let's take it from the top...
The goal is to empty the Sistine Chapel without being detected. You can use a similar process to wield the Papal Staff as a weapon to kill others; this is shown at the end.
If you haven't seen it already, I recommend first watching and reading this article on the "Non-story Rodrigo Borgia Assassination," which has highly relevant information: