I just had a quick look in Lightroom. In 2010 and 2011, it was the 300 f/2.8, due to all the wildlife images. I haven't done much wildlife shooting yet this year though, so it is the 24 f/1.4 MkII (which is only about 4 months old). What is interesting though is how my lens use has altered over the past two and half years (it probably changed before that too, but I recently had to clear out my main hard drive, so it isn't as easy to check - I suspect the 17-40 featured highly though, as did the 100-400). In 2010, my second most used lens was the 100 macro (original, non-L), closely followed by the 24-105. In 2011, the macro and 24-105 were reversed, with the 135 f/2 closely behind. It reflects the type of shooting I have done, as I have found less opportunities for macro work and I fell in love with the 135 (a bit like I have done with the 24 MkII since).