200mm f/2.0 you can't beat magic
+1
That's your everyday goto lens?
Yes, If I go "light" ;-) (only one lens) + not knowing exactly what I will be shooting...
200/2 produce the best subject isolation and is usable on 2, if the sun goes down...
For an evidence: I do not go to shoot every day - 99% of the time I'm shooting at weekend.
(I usually ride my bike slowly thru my hometown... along the river... only one lens [+body] sitting in my backpack.)