ClipTTL is an easy to use, portable application to clear your clipboard history.
ClipTTL prevents accidental copy and pastes if that's a problem for you. Being portable, double-click it any time, and you will find it in your system tray. Right-click on the icon and select Clear now or Exit.
That's it! If you find that you copy and paste into the wrong places frequently, this is a simple, freeware solution.