My Chrome extensions these days, from left to right…
Xmarks to sync bookmarks. (But not passwords; I use LastPass for that.)
AdBlock to, well, block ads.
When someone jokes about the latest bizarre ad that Facebook showed them, I’m like: Ads?
Note: I do unblock ads for specific sites I want to support.
LastPass to manage passwords.
If I were forced to choose just one, it would have to be LastPass. It’s the only realistic way to Do the Right Thing with passwords. Such as creating sufficiently strong passwords. And not reusing the same password across multiple web sites.
It’s also the only sane way to use such passwords on mobile devices.
It’s available for all major browsers, for free. To also use on your mobile devices you pay a fee per month.
You can set it up to use two-factor authentication: something you have (e.g. your phone) as well as something you know (the password).
Music Plus for Google Play Music
Although I’m mostly using Rdio these days to discover music, what I’d already purchased is stored in Google Play Music.
Ghostery to block a variety of “trackers”. My most-recent addition.
The must-have extension is LastPass.