Quick tip which was published on the Google blog:

If you’re like me, you will send your contacts and even yourself quick one-line emails, sometimes with the the quick note in the subject line only. At the moment, when you try sending an email with only a subject line (no message), Gmail prompts you and asks you if you really want to send the a blank message body. Now there’s a way around it: add “EOM” to the end of the subject line.

Example:

Coffee at 9:30? EOM

More ways to be efficient. Excellent work, Googlers!