I usually ignore it, unless, like others have said, it is actually harming my family, myself, or someone else.
As for line cutters, others have said they don't let them pass....I do.
But I get loud and make it a point to embarrass them so everyone knows they're coming through.
It's even worse for them then to have to stand in line ahead of others that they cut, with all eyes on them.
It happened last year to us on Peter Pan.
A couple of girls, I'd say about early 20's, started cutting through, saying they were meeting up with their party (which I can't stand, but ok)
They got about 3/4's of the way through the line when they stopped.
I'm thinking they met their friends or family at that point.
As I'm watching them giggle, I realize they were by themselves and just cut through everybody by lying.
My head was ready to explode.
So I yelled out to them sarcastically (and I'm 6'7" so they couldn't miss)
"Did you find your friends? Where's your friends?" (Their faces turned red)
"Ohh so you basically cut every family because your time is more important? Ok cool. Thanks. Have a nice day"
Then as the queue winds around back and forth we wound up right near them, in perfect ear shot, and I explained to my daughter (4) what cutting the line was, and how we don't do that, because it's not nice to others.
The mortified look on their faces was priceless.