7. Search autocomplete
A small but potentially extremely handy add-on. Search autocomplete provides search suggestions for contacts as you type in the search box - very useful to find emails from a particular contact quick smart.
8. Quick links
This affixes an extra box to the left-hand column in Gmail that gives you a single-click access to a variety of bookmarked URLs. This is most useful for frequently-used searches, though you could use it for other resources you might commonly use.
9. Forgotten attachment detector
We've all done it, we've all been annoyed by it. This tool stops you from forgetting attachments by checking your mails for mentions of files in emails with no attachment. Save that face!
10. Create a document
If you've enabled Gmail keyboard shortcuts, you can create a Google Document automatically from an email conversation. Simply press "g" then "w".
11. Multiple inboxes
This clever tool enables you to add multiple lists of emails in your inbox. That means you can show a saved search, or messages with a certain label or starred messages - all at a glance.
12. Mouse gestures
We like this a lot. Enable this add-on and you can use your mouse to navigate with gestures. Holding right-click and moving the mouse left takes you to a previous conversation, while an up movement will take you back to the inbox.