When I was helping out at my local gun club we used Hoppe's exclusively to maintain around 230 rentals. That was everything from revolvers to machine guns. We used Mil Spec grease to lube the machine guns and light gun oil for everything else. I personally use more Hoppe's then anything else for my own maintenance but I prefer CLP for revolvers. I like to periodically give them a squirt or two down in to the working parts and let the excess drain out. This IMO saves you from having to remove the side plate.
Jim

Ammonia has been mentioned a few times.
I just wanted to post the CAUTION from my M&P Shield owner's manual [PDF]:

It also says:

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Be safe. Live long & prosper.

Keystone #2 not being readily available, I prefer Corrosion X.

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and what his trumpet saith