Google, the one stop shop for everything.
Looking for a website you forgot the url? Google
Looking for answers to the professor's ridiculous question? Google
Looking for pron? Google
Trivial knowledge you more than likely never need to use? Google
I bet you the cure for cancer is on Google, you just need to scroll through all the results! =P
I use Ecosia because they donate to forest conservation effort each time you use it. It runs on Bing, so I suppose Bing is my answer to the above question.
email... gmail
porn... google images
buy something?... google shopping
what is this in japanese?... google translate.
social network?... google+/fb
fb's rival?... at best google
answer to the missing 3%? google