I was going through the training games played yesterday and came across a beautiful example of a 'Mutual Blunder' in chess! Before we proceed let us examine its definition - 'Mutual Blunder' is a move where one player blunders and his opponent, who is expected to take full advantage of this mistake reciprocates!

The best example of 'Mutual Blunder' is game Game 6 of Sochi WCC between Anand - Carlsen:

 

The text position was reached after White's 26th move wherein Carlsen erred with 26.Kd2? and now, Anand could have simply grabbed this opportunity with both the hands: 27.Nxe5! Rxg8 28.Nxc4+ Kd3 29.Nb2+ Kd2 30.Rxg8 -+

However, Anand reciprocated the mistake with 27.a4? Carlsen hurried back to safety with 27.Ke2.

The mistake affected Anand much more and he simply lost this game (and the match!): 

It is amazing that how ideas keep repeating in chess! A similar story was witnessed in the training game played between Ved Shubham (1344) v/s Rohnit Amin (1471):

 

Shubham 23.Rxa5? is a mistake and Rohnit could easily won the game with a pretty combination: 23.Qxf3! Bxf3 24.Rh2+ and thereby regaining the Queen with material advantage. However, Rohnit reciprocated by playing Rh2 one move earlier! As in Carlsen - Anand, White scurried to safety with 24.Qe2 and went on to win the game after 43 moves: