Tab into edit mode (like Blender)

[Intuos5]

This may be a controversial one, but I quite like Blender's 'tab into edit mode' paradigm. I sometimes accidentally exit out subobject modification by pressing the numerical key corresponding to the current object level (e.g. "2" for edge when in edge mode). By adding the option in the user preferences to enter/exit subobject mode with tab only this would save a little bit of time for each accidental exiting and re-entering subobject mode to continue modeling.

[Swordslayer]

There's already the Sub-object Selection Toggle (Ctrl+B by default, but you can map that to Tab if you want) to enter/exit the last active subobject mode. Together with the 'Multi' preview selection mode that takes you to the matching subobject level depending on whether you clicked a vertex, edge or polygon, that's all you'd need.

Also, if you're accidentally exiting subobject mode by pressing the same key twice, you could just as well remap the shortcuts from subobject level toggles (enter/exit) to non-toggle shortcuts (enter only) – if you can't find them, you can just type subobjectLevel = 1 and select+drag that text to a toolbar to create custom macro for that in drag&drop category (you can then delete the button from the toolbar) and assign that as vertex mode and repeat for other modes/numbers. To exit the subobject mode (since you'd now need that as well), you'd use Object Level shortcut (or 0 for subobjectLevel value).

[Intuos5]

For those who are interested, a working script to achieve this proposal can be found here: https://forums.autodesk.com/t5/3ds-max-programming/tab-into-edit-mode-like-blender/m-p/9696958.
You can then map 1/2/3/4/5 to the subobjectlevel commands in the Hotkey editor and Tab to objectlevel (this is also a default command in 3ds Max, so it does not necessarily require the first script).