I worked a couple of them; but the station that intrigued me the most was GM100RSGB, the Centennial Special Event Station for the RSGB from Scotland. At 1914 UTC, they were loud into New Jersey on 20 Meters, and I was able to work them with 5 Watts very easily. According to QRZ.com, this is what their QSL looks like:
The Centennial for the ARRL occurs next year. I wonder if the League will petition the FCC for a special anniversary call sign for W1AW for next year?
72 de Larry W2LJ
QRP - When you care to send the very least!