1) Viennese Waltz - when done well it looks absolutely beautiful. Loved Sophie & Brendan's, Katie & Anton's and, of course, the afore-mentioned Alesha & Matthew's. Hell, I even loved Kellie & Kevin's last year!
2) Charleston - fun, quirky and almost anyone can pull it off. Love the character of it. Peter & Janette's was amazing - there, I've said it.
3) In contrast to the Charleston, the technicality of it is fascinating. Vincent and Flavia's and of course the Ramps and Karen's stand out in the memory.