Ctrl+Z

Undo

Ctrl+Y

Redo (after undo) or Repeat (e.g. when applying formats)

Alt+3

Undo list (via quick access). Use Arrow Down to extend undo range.

Alt+4

Redo list (via quick access). Use Arrow Down to extend redo range.

Alt+Enter outside edit cell mode

Repeat last action. E.g. try to set a cell bold with Ctrl+B, then go to a different cell and press Alt+Enter; great to cascade formatting across multiple cells

Ctrl+X

Cut cell(s) to clipoard

Ctrl+C

Copy cell(s) to clipboard

Ctrl+V

Paste cell(s) from clipboard

Ctrl+plus

Insert Paste - Paste cell and push content downward or rightward. Works great for entire rows and columns.

Ctrl+Alt+V

Open Paste Special Menu (requires a prior copy to Clipboard)

Ctrl+Alt+V, then V, Enter

Paste Values

Ctrl+Alt+V, then T, Enter

Paste Formats

Ctrl+Alt+V, then E, Enter

Paste Transposed

Ctrl+Alt+V, then W, Enter

Paste Column Width

Ctrl+Alt+V, then U, Enter

Paste Values and Number Formats

F3

Paste a defined name into a formula