Perhaps your favorite trick most http://usa.autodesk.com/autocad/ - AutoCAD users are not aware of is how easy it is to locate the middle of a rectangle or a location fast and accurately by using temporary tracking points and http://docs.autodesk.com/ACD/2014/ENU/files/GUID-665DC37F-8C3E-414A-9369-72A13C0BE07A.htm - Object Snap Tracking (Otrack F11) and Object Snaps ( http://docs.autodesk.com/ACD/2014/ENU/files/GUID-CF5780AD-D1AB-4526-9608-83D7952749E7.htm - OSNAPS F3.)

Share Your Tips
But I know you have many tricks and tips you tell your fellow users or just have not shared but deep down you really want to, so in the spirit of sharing and making us all better AutoCAD users please share your tips with the fellow daily http://autodesk.blogs.com/between_the_lines/ - Between the Lines blog 20,000 readers. Mention your AutoCAD blog, Twitter, user group, website, book, training videos, company or a shout out to your kids and family. You may not get fame or fortune but you will be read and I might find some prizes to send out.

Post your tip, trick or AutoCAD prank to the comments or mailto:shaan@autodesk.com?subject=Between the Lines AutoCAD Tip or Trick - email me and I will post them all to the body of this post.

AutoCAD Tips, Tricks & Pranks (Updating constantly from emails and comments):

Need to toggle off OSNAP, POLAR & OTRACK to get the equivalent of the old "None" OSNAP (Object Snap) override from AutoCAD R14 and earlier?

Use a temporary override to disable all snapping and object tracking.  Shift + D (or Shift + L for the left-handers.) – Shaan Hurley

Ctrl+Double Click on an attribute
Allow you to edit an attribute (including multi-line attributes) in place.
-Steven LaKose

Change someone's MTJIGSTRING to say something weird. Go to Bob's machine and set MTJIGSTRING to "Hi Bob!" That got a few good reactions.

Little more sinister: UNDEFINE a few often used commands like move, copy etc.

Here is a conversation I started on this topic, with quite a few nice suggestions from seasoned users: http://forums.autodesk.com/t5/The-Break-Room-Non-Technical/What-s-your-favourite-ACAD-prank/td-p/3759864 - http://forums.autodesk.com/t5/...
-Mark Green

Easy prank: draw a wipeout and hide frames.
Somewhat harder prank: change plotstyle to plot all with dotted linetype.
:-) TGIF! 
–Harold

The AutoCAD Vault Browser? What? yup, there is one. The familiar AutoCAD External References palette mimics the Inventor Vault browser once you have logged into Vault within AutoCAD. You can check your files and its references or attachments In or Out from the Xref browser. I was surprised to find a lot of AutoCAD users didn't realize this can permanently used the Vault ribbon tab or typed all their commands. However, neither of this approaches gives you the visibility of your data the Xref palette does.
Go check it out if you haven't already. ;-) -Scott Moyse

While in layer manager. When you create a new layers property always add in a wild card layer* to each one. This way when you are in the layer manager and a particular layer property and create a new layer AutoCAD will let you remain in that layer property without kicking out. –CivilGuy

Spread the word to others and your users groups to share their best tips!

Cheers,
Shaan