In a recent usability study, participants routinely did not recognize that "Toggle Breakpoint" would perform the operation they wanted (to 
quickly set a breakpoint on the current line).

When asked about why they had ignored this command, one participant said that 
  the command sounded like it would transfer them to the next breakpoint, while 
  another said that it sounded like it would be used to disable an existing breakpoint. 
  Another participant clearly thought "Toggle Breakpoint" could only 
  be used on breakpoints that already existed (consistently using "Add Breakpoint..."
  to add a breakpoint, and "Toggle Breakpoint" to remove one).

I'd recommend renaming this item to "Insert/Remove Breakpoint", or 
  if possible make it context sensitive so it says "Insert Breakpoint" 
  and "Remove Breakpoint" depending on whether there is already a breakpoint 
  on the line. These names have the benefit of sounding like they will create 
  a breakpoint, but still seem distinct from the "Add Breakpoint..." 
  command.