Another handy script for nuker's. Hope this will help you friends.
flop and flip
Updated: 23 April 2013
Author: satheesh
Compatible Nuke versions: 5.2 or later
Compatibility: Linux, Mac, Windows
Fixed node selection issue.
For doing flop or flip you need to add mirror node and connect it with a (any) node, then constantly check and uncheck the Horizontal or vertical knob. Finally you have to delete the mirror node.
flopFlop script dosen't need above step 's. Now you can flop & flip your current viewer by hotKeys. Just press ctrl+F for flop, ctrl+shift+F for flip.
Add following lines to your menu.py:
import flopflip
menuBar.addCommand('Edit/Node/flop', 'flopflip.flop()', 'ctrl+f')
menuBar.addCommand('Edit/Node/flip', 'flopflip.flip()', 'ctrl+shift+f')