Do you enable v-sync ?

Nope, I turn it off. I run windowed instead of full-screen.

Always on.

I turn it on because the tearing is awful on my computer

Always depends, 90% of the time it's off because I find it causes issues with performance. But there's a few games where screen tearing is so bad I turn it on.

Generally no,but it's good for games which my computer can run smoothly to avoid stuttering but in most cases i don't use it because my GPU isn't strong enough

Nah.

It depends on what game I want to play.

G-Sync all the way!

Always off unless it's an old/easy game that doesn't use much resources.
Edit: Actually, I disable v-sync by default in the graphics card driver.

Most of the times not, but some games look like crap without it. Those are the only instances I turn it on.

Never
it's bad for performance and causes input-lag. Exceptions may exist though.
FPS cap is far better.

I turn it off unless I actually notice some tearing

Usually not, but I turn it on/off if something strange happens in a game. Interesting thing I encountered was in Assassin's Creed 1 where on one spot without V-sync enabled, Altair would do the leap of faith and kill himself by missing the hay cart. Repeatedly, until I tried turning V-sync on. In The Darkness 2 during some vent crawling I got an invisible obstacle that was solved also by either turning V-sync on or off.

Always, but now I use GSYNC. I can't stand screen tearing.

It depends on the game. In a game where the input lag doesn't matter I will turn it on. When off, I usually use Afterburner to cap the fps somewhere around my refresh rate where it has the least noticeable tearing.

No. I don't know how to turn it off on my Android tablet.

No, generally brings issues and the response is better without it; unless the game suffers severe screen tearing.

G-Sync!

Depends on the game - last game i remember trying ... instantly activating it > Wasted,
that crap was tearing everywhere without V-SYNC.

no i have 144 hz monitor with free sync

I still don't understand entirely what it does. So no.

Quite the opposite, I usually turn it off in the settings :D

Only when my gpu is overpowered, like when I got gtx560 in 2012 and still played L4D2 and had 120+ fps on 59hz monitor. But I'm not used to it as I most of the time have sub par gpu that bothers to achieve 60 fps.