I often use
J to join the current line with the one below:
J Join [count] lines, with a minimum of two lines. Remove the indent and insert up to two spaces (see below). Fails when on the last line of the buffer. If [count] is too big it is reduce to the number of lines available.
Is there a shortcut key for joining the current line with the line above?
Needless to say,
kJ does the trick; I just wonder if there's a built-in shortcut for that.