135L if you've got the money and the 100mm f/2 if you don't. The macro is a good option but doesn't have the same look as the other two.
Thank you all for your comments, there are one or two options there that I hadn't previously considered. Especially the one about converting it to IR. Do you honestly believe that will add value to this camera???
RLPhoto - no idea why dance receptions are relevant to this...