If you collect insulators, these are must-haves:
1) Oxalic Acid (Wood Bleach) - Great for cleaning most filthy glass insulators. Just soak them in a bucket of this for a few days (or weeks for the really filthy ones) and they'll come out looking brand new. Warning: Do NOT use with carnival, flashed amber, or opalescent glass! Be sure to read this page on proper insulator cleaning!
2) Museum Gel - This stuff is awesome for keeping your insulators on glass shelves and preventing them from moving around or falling off. Use them between two-piece transposition insulators instead of those ugly wooden dowels!
3) Collapsible Hand Truck - These are lifesavers for toting all those boxes of insulators around, especially going back and forth to an insulator show. Whether you buy or sell, you definitely appreciate having one of these...