Show exposé/"All Application Windows" from the dock
Found a way to (sort of) do it: https://apple.stackexchange.com/a/76103/38367

The following command will enable the mouse scroll-up on an app icon to open exposé:   

defaults write com.apple.Dock scroll-to-open -bool true
killall Dock


More info on: http://osxdaily.com/2011/11/30/enable-hidden-stack-gestures-mac-os-x-lion/