What I used:
Paper Mac, around which everything is based ("A mini paper Mac? What would Largo do?")
Light brown construction paper for the boxes. The bottom box is 2"2"3", folded up from a 4"10" rectangle (with an extra 1/2" tab on one end). The middle box is a 2" cube, from a 4"8" piece with tab. The top cowling is 2 1/2" tall, 2" wide, and 1 1/2" deep, folded up from a 1 1/2"9" piece, plus the added 1/2" overhang in front and the little horn things.
The tubes are 3 1/4"2" and 3 1/4"4" pieces of standard white paper, rolled up around a 1/2" diameter pen barrel and secured with tape.
The nosecones are colored typing paper, half circles with a 3/4" radius, rolled up and secured with tape, then glued into place in the tubes.
The ears are more colored typing paper, little 1"3/8" bits.
And silver paint marker as a stand in for duct tape.
(Prototype standing over to the side)


I used a glue stick initially to get the boxes and Mac folded up, but the stick I had was old and crappy so I switched to white glue for the remaining assembly. Used very sparingly, I might add, you only need a little to get stuff to stick and too much risks making a mess of things.
Everything folded/rolled, ready for assembly:


The smiley face just makes it more awesome, but the guy released the source file so you can leave off the face like it was in the comic or change the face to whatever.