My top 5 are modeling area biased:
1) Unfold op and the Regularize tool (especially in 2014sp2, since the Regularize tool doesn´t stop at shell borders) 2) Everything that´s part of the "M" shortcut/workflow (Sliding edges/points/faces, etc). Adding eges. Splitting edges. Loops. 3) The render region. The render region. The render region. 4) The operator stack. An envelope can swims atop massive changes to a topology and still interpolates existing wheights nicely. Great for testing and working out shape/topology on a mesh - you´re not restricted to being stuck in the bindpose. Also helps prepping a mesh copy for painting/sculpting. 5) Copy&Paste UVs. Bake to another UV set. Gator/Rendermap. Cheers, tim
