If a competition is held among the most knowledgeable Search Engines, there is no doubt Google will win it. Although very young, this engine has acquired immense popularity and won considerable amount of respect and credibility among people of all ages. Google runs the fastest with the most number of hits in a single click.
NOTE: A few of these apps, such as Google Keyboard, are not supported on older versions of Android.
List of all Google apps
ADK 2012
AdWords Express
Android Auto
Android Device Manager
Android System WebView
Androidify
Android Pay
Android TV Remote Control
Android Wear
Arts & Culture
Beacon Tools
Blogger
Calculator
Cardboard
Cardboard Camera
Chrome Beta
Google Chrome for Android
Chrome Canary (unstable)
Chrome Dev
Chrome Remote Desktop
Clock
Crowdsource
Cloud Print
Contacts
Creative Preview
DoubleClick for Publishers
Expeditions
Messenger
Wallpapers
Gmail
Google+
Google Admin
Google AdSense
Google Allo
Google Analytics
Google Apps Device Policy
Google Authenticator
Google Calendar
Google Camera
Google Cantonese Input
Google Classroom
Google Docs
Google Drive
Google Duo
Google Earth
Google Edu Device Setup
Google Fiber
Google Finance
Google Fit
Google Gesture Search
Google Goggles
Google Handwriting Input
Google Home
Google I/O 2016
Google Indic Keyboard
Google Japanese Input
Google Keep
Google Keyboard
Google Korean Input
Google Maps
Google My Business
Google News & Weather
Google Now Launcher
Google On
Google Photos
Google Pinyin Input
Google PDF Viewer
Google Play Books
Google Play Developer Console
Google Play Music
Google Play Movies & TV
Google Play Newsstand
Google Play Games
Google Play Services (API)
Google Santa Tracker
Google Search
Google Sheets
Google Slides
Google Springboard
Google Street View
Google Talkback
Google Text-to-Speech
Google Translate
Google Trips
Google Voice
Google Wallet
Google Zhuyin Input
Hangouts
Hangouts Dialer
Inbox by Gmail
Intersection Explorer (helps visually impaired users explore their neighborhoods through Google Maps)
Jump Inspector
Messenger
MyGlass (companion app for Google Glass)
My Maps
Phone
Project Fi
Snapseed
Spaces - Small group sharing
Street View on Google Maps
Who's Down - Spring 2016
YouTube
YouTube Creator Studio
YouTube Gaming