Apple - Is there a keyboard shortcut for launching Activity Monitor?

Not by default, but you can create one in System Preferences --> Keyboard --> Keyboard Shortcuts. Or you can use spotlight:

• type ⌘ + space

• start typing "activity monitor"

• as soon as activity monitor is highlighted in the spotlight list, hit return

Save in AppleScript Editor and assign a shortcut in FastScripts or some other way:

tell app "Activity Monitor"
    reopen -- makes a new window if there are no existing windows
    activate -- brings the app to front
end tell

Create in Automator an Action to launch Activity Monitor:

Then in System Preferences -> Shortcuts Tab -> Services set a keyboard shortcut for the created service: