Quality hollow ground screwdriver bits, good torx and hex wrenches that won't strip bolt-heads, solid vice with soft jaw attachments, roll pin and regular punches without long ends that break, torque wrench and screwdriver, nut drivers....all necessary but the MOST used items for me, over 50 yrs old, headlamp and magnified or reading glasses. Also, I have learned the hard way to always put masking or vinyl/electrical tape around area being worked on so that I don't gouge/scrape surfaces. Pin removal on FN509 compact for APEX trigger replacement, without the jig, stands out in my memory. Even the dog ran out of the room from the cussing!