Edit Mode - Keys

MESH
Faces Menu [f]
Specials Menu [w]
Convert Tris to Quads [Alt + j]
Convert Quads to Tris [Ctrl + t]
Convert Mesh/Curve [Alt + c]
To Sphere [Shift + Alt + s]
Switch Select Type [Ctrl + TAB] //point, edge, face
Fix Normals [Ctrl + n]
Merge Vertices [Alt + m]  // collapse
Ring of Vertices [Ctrl + r]
Extrude [e]
Extrude Edges [Shift + e]  // mean crease
Select Linked Vertices [Ctrl + L] // at least one vertex selected
Select All Adjacent Vertices [Ctrl + NUM PLUS]
Deselect All Adjacent Vertices [Ctrl + NUM MINUS]

Separate as Mesh [p]
Join Mesh [Ctrl+j]

CURVES
Handle Menu [v]
Close the Curve [Alt + c]
Convert Mesh/Curve [Alt + c]