I can't really say what I use the most.
For mountain bike events it's been the 24-70mm and the 28-135mm with a few of the 100-400mm thrown in.
For birds it's exclusively the 100-400mm.
For landscapes it's the 10-22mm and the 24 -70mm mostly and occassionally the 100-400.
Portraits it's the 24-70mm or the 50mm usually but I'll occassionally play with the 100-400 again also.