I agree some of those may not be the most exciting, but I think the 'select similar polys
' can come in pretty handy.
BTW In contrast for angle based stuff .. the following is SOO useful for quickly selecting specific edges for beveling or creasing or whatever in one go (!)
(from RRRay's magic bag
mHard Edge Marker Author: Martin Yara
Run it from the Model - Modify Component menu on the left. You have 3 buttons: Select - It will select all edges whose neightbor faces have an angle superior to the one specified in the angle option. It works with objects, and with specified subcomponent selections. This is based on »Select Hard Edges« by Christopher Peltz, but working a lot faster. Hard - Mark selected edges to Hard, delete edge clusters and freeze only the mark hard edges operator in the selected object. Soft - Unmark hard edges to soft.
Instructions: Drag & Drop the xsiaddon to the XSI Viewport (you can drag & drop directly from the link) Versions: XSI 5.11 and later
local backup: mHardEdgeMarker.xsiaddon
author blog: http://myara.blog.fc2.com / download: /mHardEdgeMarker.html