Contextual Menu Keyboard Shortcuts
You can set shortcuts for some context shortcuts, specifically anything that's a service. Most app-specific context menu items aren't services (although some, such as services to modify a file in a particular app are), so they can't be assigned shortcuts. So it depends which items you want a shortcut for, but it's doable.

To add a shortcut for a service, open Keyboard Preferences, click the Keyboard Shortcuts tab, and select Services in the left pane. Then look for the context menu item you want in the right pane, click it and you'll get an option to set a shortcut.