Back when Avatar was in the movies i saw it with some friends, 2 of them biology students at the time and they went ballistic when they saw Sigourney Weaver put small probes of some stuff into test tubes with a handheld dropper thingy.. "That's not how you do it!!!" 
I let such small things slide, it's very minor and not important to the story. However it irks me sometimes when it's a major faux pas or when realism is ignored because the writing is lazy (i like the show Supergirl very much but it's one of the worst offenders.. recently one character put on a power enhancing exoskeleton (think Tom Cruise in Edge of Tomorrow) and she hit someone full force with her bare fist.. it should have pulverized every bone in her hand).
Another thing that i never realized was a mistake was the widespread usage of power paddles whenever someone#s heart has stopped and they need to jumpstart it again like you would do with a car. I learned that's not how it works.. paddles are used when the heart beats in a dangerous arrythmic way and it actually stops the heart so it can restart in a natural and hopefully correct way, so it's more like a reboot of the heart instead of jumpstarting it. It's especially irksome of some medical show claims they have doctors on staff to help them with realism and then they pull this off consistently.

I let such small things slide, it's very minor and not important to the story. However it irks me sometimes when it's a major faux pas or when realism is ignored because the writing is lazy (i like the show Supergirl very much but it's one of the worst offenders.. recently one character put on a power enhancing exoskeleton (think Tom Cruise in Edge of Tomorrow) and she hit someone full force with her bare fist.. it should have pulverized every bone in her hand).
Another thing that i never realized was a mistake was the widespread usage of power paddles whenever someone#s heart has stopped and they need to jumpstart it again like you would do with a car. I learned that's not how it works.. paddles are used when the heart beats in a dangerous arrythmic way and it actually stops the heart so it can restart in a natural and hopefully correct way, so it's more like a reboot of the heart instead of jumpstarting it. It's especially irksome of some medical show claims they have doctors on staff to help them with realism and then they pull this off consistently.