Scribes. For marking work, sharpies are generally good for only one thing - providing a contrasting film for scribe marks. Everybody who works in the mechanical area should have a scribe. I use two types - a carbide tipped scribe and a steel machinist's combination scribe. The carbide scribe is generally more useful, but the L-shaped tips of the machinist's scribe are sometimes useful. Most good combination squares have a small scribe in the head, but these are usually too small, and they get lost.
Transfer screws. The team has a set of transfer punches, which have occasionally been very useful. A related item is transfer screws. These look a little like a set screw, but instead of a socket, there is a hardened centered spur sticking out. You normally use these in sets. For example, if you want to drill the holes to match the mounting holes in a bainbot transmission, you would put four transfer screws in the 1/4-20 threaded holes of the transmission such that the tips were all in the same plane and then you would set the transmission onto the thing you wanted to drill holes in and give the transmission or the plate a tap with a mallet. The spurs mark the places to drill the holes. The one on the right, called a spotting screw, also marks a circle the size of the hole to be drilled and is nice because it has a real head so you can screw it all the way in for planarization. This things cost $1-$2 each, and often come in sets. A set like the one below in 10-24, 10-32 and 1/4-20 is $22.