New Google Account using existing Email Address
You can create a new Gmail account using the same address you have. Gmail regular sign up method uses your gmail.com address as your Gmail mail id and google account username .with a special sign up process you can create a new Gmail account for the same Gmail id you own. Gmail Sign up without Gmail id
Google can guess your Age and Interests
Google can guess your age, gender, interests, and language based on your google search and the sites you visit. Google use these details to serve you ads relevant to your interests. Use this link to see what Google think about you . Google Search History
Google records every search words that you ever used on Google search. This may seem funny but believe me Google keeps a log of every google ad that you have clicked on websites. If you ever used google audio search you can view them also. Google Search history
You can download your google account Data from google. your Gmail Emails, photos, contacts, and YouTube videos are available to Download.to Get your Data from google go to Google Takeout Page and Download .
View your location History on Google Maps
You can view your current location on your android Device if you are moving it will show you how fast you are moving. And you can view your entire location History on your Google Maps Website. You can export your location history and view it later on Google Earth or google Drive. Google Maps locations history.
Prevent Your Google Account from Termination
As per Google program policies you must log in to your Gmail account at least once every 9 months otherwise Google will terminate your account. If you own multiple accounts this can be a problem. To prevent this set your primary G mail account as your email recovery for your secondary accounts .so Google will send you reminders frequently to log in to your other Email. View inactive Accounts.
Google Account Activity
You can view every Devices that used to log into your Account. The activity reports show I.P.Address and their Geographic location, the geographic location won’t be exact location. View Google Activity log
Regain Hacked Google Apps Account
This trick is for Google Apps users, if your google account get hacked you can rest your Account Admin password. You need to verify your domain name by creating a Cname record in your DNS.to reset your account password go to this link https://admin.google.com/yourdomain.com/VerifyAdminAccountPasswordReset
Note: replace “yourdomain” with your own domain name
Google DMCA complaint
If your content is used without your Permission on another google product websites like Youtube, Google+, Bloggers etc. you can raise a DMCA complaint against that website. Your complaint will force the user to remove that content .it also remove websites from Google Search Results. DMCA Complaint Page .