Pete Davidson Helps David Blaine Perform Gross Magic Trick

David Blaine got an assist from Pete Davidson for a magic trick Friday night at his Las Vegas show, and TMZ has obtained video of the most shocking moment.

Check it out for yourself ... David kicked things off at his Resorts World performance by escorting Pete and his friend from the packed crowd to the stage, where 4 cups were lined up across a table ... and Pete was asked to choose one of the cups ... which contained an object that would be used in the trick.

Pete picked the right cup and David uncovered the scary object -- which was a large ice pick. Pete and his buddy confirmed its sharpness by touching the spike, and told David ... "Yup, you're nuts."

Then, while Pete duct taped David's eyes closed ... Pete's friend arranged 3 of the cups on the table and placed the needle sticking upward under one of them. The now-blindfolded Blaine then put his hands over 2 of the cups, and crushed them -- and while the audience shrieked in horror ... David escaped injury.

Of course, the ice pick was in the 3rd cup ... otherwise, this would be a much different story.

The danger wasn't over, though ... David asked Pete to stab him with the ice pick, and he did -- pushing the needle through David's arm until it came out the other side. The crowd was grossed out, but also impressed ... and, no doubt, confused.

David didn't seem bothered by the ice pick dangling from his arm-- and even brought a boy on stage to have him pull the needle out of his bicep.