The following are some useful things I've found:
Edit Mode1) Remove Doubles
I'm sure you've used this before, but you probably never looked in the toolbar to see what settings there are. The default setting usually works for doubled up vertices, but you can also use it to merge vertices that are close together:
|(press F6) After|
Most of us have separated object an single object into multiple objects by selection. Not many people use the other two options. Separate by material and separate by loose parts. Separate by material will split objects up based upon which material they have. Separate by loose parts will separate all parts that are not connected to anything into there own individual objects. For example:
|A simple array|
|In edit mode after applying the modifier|
|After separation by loose parts|
3) Select Nth
Select every nth number of (i.e every other). Useful for saving time when doing repetitive selecting.
4) Select loose Vertices/Edges
Selects vertices/edges that are not connected to anything. Good for deleting hard to find (and non-usable) geometry
5) Select More/Less
Shortcut key is CTRL-+(for selecting more) and CTRL-- (for selecting less).
Selecting more will grow the selection by one vertex. Likewise select less, will shrink the selection by one vertex.
Object Mode1) ALT-RIGHTCLICK
Few people know of this hidden tool. When you press ALT-RIGHTCLICK, a menu will pop up naming all the objects near the cursor.
This tool is immensely useful in highly populated scenes or scenes with tiny objects.
2) Randomize Transform
This one is in the menu (Object > Transform > Randomize Transform), it's the next best thing after the grease scatter. As it's name suggests, it randomly places the selected objects throughout the scene.
You have to set the (location/rotation/scale) limits using F6, otherwise nothing will change.
3) Select Random
Another great randomization tool. It's position is Select > Random.
4) Zoom Border
Helpful when you run out of zooming with your scroll wheel. Shift-B.
5) Quad View
Pressing CTRL-ALT-Q will toggle quad view:
Notice that quid view will lock all of its views, except for the camera view. This is sometimes useful if you find yourself setting up side and front views, and continually changing them the angle views, out of habit.
Quad view also helps save space, you only need one toolbar or properties bar, instead of one per view.
Do you know of any good hidden shortcuts? Post them in the comments below!