Stalls tickets for the first three performances of the Royal Opera House's Elektra are up to a third off.
Pick a date from this list, press BUY, then type the discount code STRAUSSELEKTRA into the box in the top right hand corner. Pick your stalls seats from the plan, then select the Last Minute offer price. (If you try to go into the ticket selection page any other way, the code may not work.)
UPDATE - reader Richard has just pointed out an even better offer from LoveTheatre: stalls seats for £58, or up to 60% off. You don't get to choose your seats with this one, but they do tell you which seats have been allocated before you pay.