A Classic, or better yet, Rambler. That's to supplement his Wave, the multi-tool he should be carrying these days. Remember, the series was filmed BL*
*before Leatherman
Remember that McGyver normally used the smaller 2 layer models of victorinox in a very minimalistic way. Often just a 74 mm model like the executive. Normally no pliers.
Should he use a leatherman the P4 or maybe juice KF4 or S2 is choser to his style.