Vim, 2 Keystrokes

vim -u NONE then run the following (-u NONE turns off customization)

i<up>

When vim is run in compatible mode the arrow keys are don't get interpreted properly. <up> gets interpreted <esc>OA which leave the following in insert mode. Which would leave (with a couple of trailing newlines)

A

i starts insert mode.
<up> exits insert mode, opens a line above and enters A into the buffer

Example of people encountering this in the wild. http://stackoverflow.com/questions/6987317/while-moving-the-cursor-across-a-vim-process-open-in-a-tmux-session-every-now-a/6988748#6988748https://stackoverflow.com/questions/6987317/while-moving-the-cursor-across-a-vim-process-open-in-a-tmux-session-every-now-a/6988748#6988748