Ryanair carried 95% leisure passengers to Frankfurt when they operated the service. (Probably so high because it was Hahn and not Main) Frankfurt has great connections to the region around it. Same for Munich - with LCC's it's not so much the city that matters but VFRs, and regional pull.
City's I do not suggest from BOH: Brussels, Luxemburg, Rotterdam, Antwerp, Dresden, Bremen, Aberdeen, Copehagen, Lyon, Dusseldorf, Hanover etc.