Go to Gmail--->Setting--->Labs--->Enable Undo Send
2 Automatically categorizes incoming Bulk,Notification & Forum message.
Go to Gmail--->Setting--->Labs--->Enable Smart Labels
3 Move the chat box to the right side of the inbox
Go to Gmail--->Setting--->Labs--->Enable Right side chat
4 Video chat enhancements.
Go to Gmail--->Setting--->Labs--->Enable Video chat enhancements
5 Enable Mouse Gestures.
Go to Gmail--->Setting--->Labs--->Enable Mouse gestures
6 Change your Theme in Gmail
Go to Gmail--->Setting-->Theme