I don't really think of any one lens as my "go to" lens at WDW. I'd say that as a general rule, my 70-200 is the lens I enjoy using the most. Here are the stats from our last trip. We took 2,421 shots with an APS-C camera (Canon 7D) and 4,747 with a full frame camera (Canon 5D Mark II).
W/ APS-C camera
0% - 15mm f/2.8 Fisheye
15% - 17-40mm f/4
18% - 24-105mm f/4
17% - 24mm f/1.4
48% - 70-200mm f/2.8
0% - 135mm f/2
1% - 300mm f/2.8
With FF camera
1% - 15mm f/2.8 Fisheye
3% - 17-40mm f/4
4% - 24-105mm f/4
34% - 24mm f/1.4
22% - 70-200mm f/2.8
11% - 135mm f/2
25% - 300mm f/2.8
Combined Usage
1% - 15mm f/2.8 Fisheye
7% - 17-40mm f/4
9% - 24-105mm f/4
29% - 24mm f/1.4
31% - 70-200mm f/2.8
7% - 135mm f/2
17% - 300mm f/2.8