First off, it is a really hard choice to make. But considering the various types of things I do, I might come up with following answer.
17 TS-E (close call between the 17 and 24, choosing the 17 because of the density in switzerland (architectural) and the good usage in landscape work)
50 1.2 (got to have a standard lens, the 1.2 is just better than all the alternatives, even though it's not the best lens ever created. to be fair, there is a lack of good 50's)
70-200 2.8 IS II (i just have to have this one. this lens gets the most use any day. perfect for portraiture, sporting events, speeches etc.)