One type of drill I use a lot are step drills. They are best thing since sliced bread for cutting circular holes in sheet metal and relatively thin stock where the the thickness of the material is less than the height of the “step” in the drill. Unlike a normal twist drill, the step drills will not thread onto sheet metal and make a mess. You get a nice hole on one side and if you can reach the back side, you can come at it from that direction and remove burrs very easily.
I keep a variety of step drills including some odd-ball drills that are very similar but stepless that I mainly for opening up some odd non-critical sized hole.
I also have several lengths of Irwin extensions that I use for holding step bits, spade bits, screw-drivers and just about anything else with the common 1/4″ interface. I’ve even plugged one extension into another to reach really remove parts and can’t even guess how many times these extensions have saved my bacon.
I’d recommend that you keep all of these handy. If you can, buy a known good brand as it will probably last longer. My problem with imported cheap bits in the past is that they dull fast. Irwin, Dewalt, Klein, Milwaukee and other name brands might be something you want to invest in if you plan to use them a lot.
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