Shift+cmd+b can cut all the clips under the play head,
it also cut where the skimmer is placed but make sure that the skimmer is above all the clips (or) disable the clip skimming opt+cmd+s.
i am using fcpx 10.0.8 version.
b – select blade tool
cmd+b – cut the clip which is in the story line (or) the selected clip (or)
shift+cmd+b – cut all the clips, it is same as clrt+v in fcp 7
*VIKRAM*
MOVIE and AD film Editor