In the mission Terminus, if you take the underground path, climb up the opening and kill the first guard with a wrench and hide the body back in the opening, the body will be marked as hidden. Climb down and take his disguise. Doing so will result in the body standing with his hands expanded, and you can't drag him anymore.
Buggy Animation (Layla Stockton)
There is a glitch in some versions of Absolution where you can become invisible to the other NPCs in the penthouse section in Blackwater Park. After the mission starts, get the Blackwater Manager disguise and get into the elevator with it. Once the penthouse section begins, get to the other side of the ledge and go to the door. On higher difficulties, there will be a bodyguard standing right outside. You can easily garrote her and dump her body. Wait for Layla and her bodyguards to pass. Follow them into the section with the museum entrance and wait for them to go. Now sneak past the guard facing the museum and take the Samurai disguise behind him. [NOTE: If 47 doesn't immediately start hiding once you take the Samurai disguise, your version of Absolution probably doesn't have this glitch] Then stop hiding and change back into the Blackwater Manager disguise. Now you are invisible to all NPCs in the level (in case you aren't, do a checkpoint restart and try again). Note that the NPCs can still hear any sound you make, so you can still distract them.