There is an adage for writing that goes like this: good authors borrow, great authors steal. I've talked about this before. The big difference between borrowing and stealing in this context - to me at least - is that when you steal something you make it your own. That means you don't just lift say Thresh from League of Legends out of League and into your game. You take the idea of Thresh, make him your own, and put your Thresh into the game. You didn't borrow Thresh.You don't have to return him to anyone in the same condition you found him.
Now I don't know about you, but whenever I'm watching movies, playing games, or otherwise consuming stories my brain is always looking for cool sequences to bring into my games. Sometimes they can't work - a lot of movies and games focus on a single character instead of a team and that changes the dynamic - but sometimes the ideas work well. There's absolutely no problem with stealing ideas from good media. Well, except one: lots of people watch good media, so when you steal from it your idea is going to be more obviously taken and players are more likely to recognize what you're stealing from.
However, if you're the type who can enjoy bad movies you'll find a treasure trove of good ideas - with questionable execution - that even if people have seen they're not going to want to admit to it. Even better, since you're watching a 'bad' movie you can likely also see what they do that makes it work (for you) but fail to work in general which will help with your own presentation of it in your game.
So watch bad movies. Play bad games (or just watch them on youtube.) Go through obscure comics. You'll be amazed at the treasure trove of things you can steal, and the monster that doesn't work well in that movie for whatever reason can be done in your game in a new medium where they can work a lot better...provided you steal it, and don't borrow it.