Ultimate way to delete your forever unconfirmed transactions

• Backup your wallet just in case
• Download Pywallet
• Run './pywallet.py --web'
• Go to http://localhost:8989 in your browser
• Fill the Delete form like this:
  
  
  • Wallet Directory: /your/wallet/directory
  • Wallet Filename: yourwalletfilename
  • Key: all
  • Type: leave 'Transaction'
  
  
• Click the Delete button
• Run 'bitcoin -rescan'
• Done, no more unconfirmed tx's