Mysteriously In and Out - The Banker (Juan Borgia)
http://www.youtube.com/watch?v=dNFxFQvDiP8
Altair92 has already shown a nice mysterious death on the Banker (Juan Borgia) using the hidden blade:
http://www.thehiddenblade.com/banker-assassination-variety-pack
The goal in this video is to get through the entire In and Out memory without being seen at all (no yellow bars) while poisoning the Banker with the blade, and killing nobody else. For added challenge, I do this without using hiding places, such as haystacks, benches, or groups of people.
Here are important details:
0:45 The brute will stop at random points along the path to look in your direction. This doesn't mean that you are seen; it's just a game mechanic to make following someone more challenging.
1:00 Drop gently to the ground to avoid the attention of the guard next to the hay cart.
1:23 The brute will often stop on the stairs and turn toward you. Stay hidden until he reaches the top.
1:33 Before jumping off the roof, peek above to make sure the archer is not looking your way.
1:46 Wait for the papal guard to take the chest and for the original chest carrier and brute escort to start walking away.
2:00 There is a guard who will start a short patrol when you are in proximity. Make sure to trigger his movement so that you won't be seen later.
2:14 There is another guard on the other side of the wall that you need to trigger, too. Wait for him to pass before you continue.
3:51 When the cutscene ends, Ezio is teleported to the middle of a group of courtesans (yet he is not blended with them due to a glitch in the game). There are guards nearby who can see Ezio, so you should immediately hug the wall when the cutscene ends.
4:00 Take a shortcut to the main room to avoid detection.
5:43 Ezio is teleported to the middle of the group of people next to the hay cart. As the screen fades from white, you should start walking out of the group so that you don't blend with them.
6:13 Again, peek above to make sure the archer is not looking your way.
6:40 Slide along the wall to avoid being seen by the guards near the entrance to the party.
7:28 When the seeker turns his back to the Banker, you can start approaching the Banker without detection. He doesn't notice you as long as you keep to socially acceptable actions. Poison him and jump over the wall to escape.
7:52 Wait by the haystack for the Banker to die.
9:00 You are already far enough away from the scene to count as having escaped.
Most impressive! 
It would be cool to do something like this on the Baron. And notice how the Banker isn't there during the scene? It happened to me before, and I noticed some things: he's somewhere nearby and isn't affected by the scene for some reason, and also he appears where he's supposed to be about a second after the scene. So if that could be manipulated it could be an opportunity for a superfast blitz. Just poison someone in the group where you will appear right before the scene. The Banker will investigate the body during the scene if he's close enough and isn't affected by the scene. If he hasn't gone away yet you could probably kill him right when you can control Ezio again!
thx! funny thing that i DIDNT notice the banker missing from the cutscene. i DID notice how close he was in the minimap at the end of the cutscene, and i was also thinking about the same superfast blitz. he seems very close on the minimap, and you have a couple seconds before hes teleported... im not even sure the poison is needed.
btw, i suspect that the borgias can be preassassinated (or at least stabbed) in this mission when they spawn at the beginning of the cutscene. i suspect that this might be easier on the xbox than ps3 due to how the different systems transition between scenes (just a guess - i could be way off).
as for the baron, the 4 seekers in front of the gate present the main challenge...
btw, i suspect that the borgias can be preassassinated (or at least stabbed) in this mission when they spawn at the beginning of the cutscene. i suspect that this might be easier on the xbox than ps3 due to how the different systems transition between scenes (just a guess - i could be way off).
I recently attempted to preassassinate the Borgias.
1. Tried hidden blade assassination but couldn't see any kill animation before the scene started.
2. Tried throwing a heavy weapon, which never seemed to get them.
3. Tried attacking with a melee weapon. Ezio just attacks them with the weapon instead of doing a kill animation. It's like with a hired group, they don't seem to take any damage.
4. Tried throwing knives special attack. Can't tell if I killed them or not. However they can be outlined in red in the scene from being targeted.
5. Tried poison for a little bit. No success. I give up for now.
Thx. I never tried preassassinating the borgias, but I've tried preassassinating the banker right before the scene. Couldn't get him with any ranged weapons, and even when I managed to get right by him when he appears a a certain waypoint when walking I couldn't do anything to him (seriously ,Ubisoft, if your going to prestage a target you should at least make it so you can't get to him). As for the Baron you're required to kill those four seekers. They automatically spot you when your close enough, so you can try throwing knives and other ranged weapons from a great distance away to avoid detection.