Numerous commands have options not listed in their prompts, hidden options. The best-known one is in the Text command:
Specify start point of text or [Justify/Style]: r
Instead of entering J, you can directly enter the abbreviation of a justification mode, such as "r" for right.
Sometimes Autodesk mucks about with the prompt wording, yet leaves in the old prompts unanounced. The best know example here is of the UCS command.
And sometimes I discover a new one, like for grips editing. Standard practice has been to press the spacebar to get through the the grips editing options: stretch, move, rotate, scale, mirror, and back to stretch again. It turns out you can get directly to them by entering their abbreviation, as undocumented by Autodesk:
***Stretch*** -- st
***Move*** -- mo
***Rotate*** -- r
***Scale*** -- sc
***Mirror*** -- mi
Even so, the whole 2D grips editing system in AutoCAD is in need of a serious overhaul, one that I hope to see in AutoCAD 2008. For example, even TurboCAD includes a rotation handle with its grips editing.