For buffing I really like the 182.
For sculpting / shaping I use the 165 daily.
For sculpting / blush the 168 will do just fine as well, however, the 165 is easier to highlight a smaller section.
For blush I use different brushes, depending on the blush and the mood. I wish there was a brush that was in between the 187 and the 188. I find the 188 too fickly for my bigger cheeks and the 187 is a bit too big sometimes. I guess the 116 is nice if you want your blush to be on a smaller area and if you want a more diffused, wider area, I would take the 129.
For powder I think you can find good cheaper alternatives (did I just say that???) but I just do not really like the sigma ones (especially the brushes with black bristles). Mine shed a bit and bled like crazy, so I just stopped using them.
Recap (because even I can hardly make sense of all that's written above), I would get the 165 (if you can find it) for highlighting and sculpting, and I guess my preferred regular blush brush would be the 168, which sculpts well too and you could make it work for highlighting, but I prefer 165 for that. The 182 for buffing and should you want a face powder brush (for an all over dust of setting powder) I would get the 134, but it''s pricey...
Other requests?