https://github.com/jezdez/textmate-missingdrawer

Changing the terminal application launched from the sidebar

By default, the “open terminal window” button launches the Terminal application. To use iTerm, run

$ defaults write com.macromates.TextMate TerminalLauncherAppName "iTerm" 

To reset back to Terminal, run

$ defaults write com.macromates.TextMate TerminalLauncherAppName "Terminal"