The Quilcom SIM-W is synth designed to simulate the Tin Whistle. It uses no samples and relies on synthesiser techniques only. Since it’s a synthesiser, the range of timbres available is considerably wider than sample sets. And it’s free!
Click on the picture to get the zip which contains 32 and 64 bit plugins and a 32 bit plugin for Windows XP users. There’s background info, a user Guide which I recommend reading and the FlowStone schematic (which isn’t needed for the plugins to work).