MacGyver's Swiss Army Knife went through a few changes over the early episodes. His first and most often used knife was a "Spartan" model from Victorinox. The knife seen in the opening credits of each episode was a Wenger, as noted by its long keychain.
MacGyver: For the past seven years I have done nothing but travel around the world getting shot up, locked up, blown up... and all I have to show for it are a couple of empty rolls of duct tape.