Pneumatic drill

I'll put in a plug for Snap-On for this particular item. I have a Blue-Point 3/8" right angle drill, model AT810 that I absolutely love. I don't know what the current available version is. Mine is about 15 years old. It is rated at 1800 rpm at a throttle pressure pressure of 90 psig. The throttle is lever-actuated rather than trigger and it has an instant reversing button. I find this is the charm of this particular drill, although there may be others that have a similar feature. It really excells in an instance where you are drilling out old threads or enlarging holes incrementally where a hand held drill can catch and jam regularly, especially in close, awkward quarters like an engine compartment. With this drill you can keep the throttle open with your thumb while at the same time instantly and repeatedly reversing rotation using your middle to tap the reverse button in rapid succession. This is impossible to do with an electric drill. Once you've experienced the easy capability of such a feature, you'll never be without it again.

Rod

It apparently is still available. See here. Pricey but well worth it.