Tip of the day: O P [ ]

That's where my left hand resides 90% of the time I'm retouching. These are the shortcuts that I use regularly off the top of my head. This is my hand positioning but it might not work for you.

Stylus has OPTION bound to front button
Stylus has CMD Z (undo) bound to back button

O - Dodge/burn tool (holding the OPTION key when dodge tool is selected is burn)
[ - Decrease brush size and cycles through options
] - Increase brush size and cycles through options
CMD + (thumb and middle finger) - Zoom in
CMD - (thumb and middle finger) - Zoom out
J (with pinky) - Healing brush
OPTION [ (stylus OPTION) - Navigate layer below
OPTION ] (stylus OPTION) - Navigate layer above
B (big reach with pinky) - Brush tool
L - Lasso tool
M (with pinky) - Marquee tool

Left hand on ASDF
CMD Z - Undo/redo
CMD OPTION Z - Undo multiple
CMD SHIFT Z - Redo multiple
SHIFT CMD X - Liquify
F - Full screen
S - Clone stamp
CMD SHIFT E - Flatten all layers
CMD S - Save
CMD SHIFT S - Save as