Legendary Acrobat( Complete Adventurer, p. 192)
You can balance and tumble much more easily than a normal person.
Balance 24 ranks, Tumble 24 ranks, DEX 21,
You can ignore any check penalties applied for accelerated movement while balancing (see page 67 of the Player's Handbook), for accelerated tumbling (see page 84 of the Player's Handbook), or for running while balancing on a narrow surface or while tumbling (see pages 97 and 103 in this book).
Without this feat, you take a -5 penalty on Balance checks and a -10 penalty on Tumble checks when attempting to move your full speed as a move action, or a -20 penalty on Balance or Tumble checks when attempting to run while balancing on a narrow surface or while tumbling.