It took me longer than I would’ve like to find this answer, so I’m posting it.
I just downloaded some Free ACR (Adobe Camera Raw) pre-sets/settings from OnOne Software. If you click through the presets in ACR, you will find that things get “additive” (pre-sets combine), so it’s important to reset your photo before checking out the next pre-set. Having to select “reset everything” from the pre-set collection, or even selecting “reset camera raw defaults” from the tiny menu (upper right) drop down in the preset pane becomes a major inconvenience. Obviously a keyboard shortcut would help, but like with so many things, Adobe doesn’t give you a keyboard shortcut hint in the drop down, so you have to figure it out on your own.
With ACR, it’s even more tricky (using a key to toggle button functionality). The answer is: click your “alt” key on a PC (“option” on a MAC) and the “cancel” button at the bottom right corner of the ACR window will toggle to “reset.”
Important and useful functionality –hidden by Adobe as usual.
EXTRA TIP: You can actually apply ACR presets from Adobe Bridge without even opening ACR… just right click the thumbnail in Bridge, then select “Develop Settings” and you have all your ACR presets (plus some other basic ACR functionality) in the popup menu. The major bummer I’ve found with this method is that only the pre-sets that will fit on your screen can be selected (there is no ability to scroll to the bottom of the list to use the pre-sets that might be “off the bottom of your screen”).