No modifier = very important action
Ctrl modifier = important action or related/inverse to the action that use the same key but without the modifier
Alt modifier = might come in handy action
Ctrl + Shift modifier = rarely useful

---Modelling---
Select Sub-Object Ring : Ctrl+W
Select Sub-Object Loop: Ctrl+E
Select Edgeloop down add : Up Arrow
Select Edgeloop up add     : Down Arrow
Select Edgering down add : Right Arrow
Select Edgering up add : Left Arrow

Grow Selection             : Spacebar
Shrink Selection           : Ctrl+Spacebar
Connect Settings           : C
Connect                        : Ctrl+C
Distance Connect          : Alt+C
Target Weld                  : T
Collapse                        : Ctrl+T
Chamfer Settings          : F
Chamfer Mode              : Ctrl+F
Inset Settings               : Q
Bevel Settings	    : CTRL+Q
Edge Constraing Toggle: "key above tab" (which in my keyboard has a different symbol than most)
Face Constraing Toggle: Ctrl+"key above tab"
Norm Constraing Toggle: Alt+"key above tab"
Attach                            : Alt+A
Detach                           : Alt+D
Bridge  	                      : B
Cap                                : Ctrl+B  
Cut Mode                      : V
Swift Loop                    : Ctrl+V
Quick Slice                    : Alt+V
Make Planar                  : Ctrl+0 (works also with Ctlr plus the 0 from the numpad)
Invert Selection            : Alt+I


---SubObject visibility---
Hide Selected                : Ctrl+H (for some reason this keybind doesn't work, despite it isn't conflicting with anything)
Hide Unselected            : Ctrl+I (for "isolate")
Unhide All                     : Ctrl+U

---Object visibility---
Hide Selection               : H
Hide Unselected            : I (for "isolate")
Unhide All                     : U


--Changed or Removed---
Viewport Background  : Ctrl+Shift+B  (assigned to free Alt+B usage)
Edit Soft Selection        : Alt+B (assigned to free B usage)
Sound Toggle               : (removed to free "the key above TAB")
Create Camera physical from view : (removed to free "Ctrl+C")
Edge Turn                     : (removed to free "Ctrl+T")
Clone                            : (removed to free "Ctrl+V")
Pan Viewport                : (removed to free "I")
Select by Name             : (removed to free "H")
Hold                              : (removed to free "Ctrl+H")
Group Attach                : (removed to free "Ctrl+U")
Orthographic user view: (removed to free "U")