Now you will know the power of the daft slides
Darth Vader has a computer on his chest, known as the 'chest computer' in hardcore Star Wars wikia circles. Its primary function is life support, to keep Anakin Skywalker's scorched body alive. But it also has buttons. And think about it: When have you ever seen Vader, or anyone else, for that matter, actually press them in the films? Never. Not even in Star Wars Battlefront. And the expanded universe doesn't count. We know this.
So what do they do? Well, seeing as Vader lived a long time ago in a galaxy far, far away, he's not the easiest person to get in touch with. But I've got a good idea what each one does. What's that? You think I'm about to make up a silly list of improbable functions? Your lack of faith disturbs me.
Plays the Imperial March
You know when Darth Vader appears on the screen and that music kicks in? Yeah, that's not the movie's soundtrack dub. That's one of his chest buttons pushed just before the scene begins, causing the music to play over the Tannoy. Everyone stops what they're doing and looks up. Imagine how important he must feel.
Who presses it? Sometimes Vader, sometimes a favoured underling.
WiFi reset button
Ever wondered why everyone is so nice to Vader? It's because he has the admin privileges to the Death Star's wifi. One button resets it, another turns it on or off. It's currently off. And he said that if everybody does what they're told, he'll turn it back on. That's power if ever I saw it.
Who presses it? Many dream of doing it. The dreams don't end well.
The lightswitch in Lando Calrissian's room
Lando doesn't know why his lights sometimes come on in the middle of the night, or switch off when he's halfway down the stairs. Vader does.
Who presses it? Actually, anyone's allowed to, though nobody else knows what it does. So they don't like to, just in case it's a trap.
Some things can't be fixed by medical science, and Vader has terrible tinnitus from all the space explosions (even though explosions don't actually make sound in space *cough*) so this button turns on pleasant background sounds like birdsong and gushing water to help him get to sleep. His favourite setting is 'children crying'.
Who presses it? Vader, or his personal droid.
A simple press of this button injects morphine into Vader's bloodstream. He actually feels fine these days, but he likes to press it anyway. It's not anything to worry about though, he can stop any time he wants. He just doesn't want to.
Who presses it? Vader. Repeatedly.
You only ever hear 'speaking into a jam jar' Vader in the films because that's the one that's the most practical. But get a few drinks in him and he might hit these switches and start speaking like C3PO, a chipmunk, a Dalek and Sean Connery. "The er forsch ish shtrong with you, Luke Shkywalker." Nobody dares tell him that his Wookiee impression sucks though. They all laugh loudly and say how much it sounds just like Chewbacca, but really it's embarrassing.
Who presses it? When he's in the right mood, it's more like 'Who doesn't'.
Mask demister (broken)
It had been a bit temperamental for a while since he spilled orange juice down his front a few weeks ago. And then he y'know tried to force it.
Who presses it? The nice man from Sith Suits R Us is having a go.
Inside that helmet, Vader's got all kinds of gadgetry going on, including a HUD. It runs on Android. Oh my mistake, it runs on the innards of a droid. Sneak up on him while he's in his quarters, and you'll likely find him repeatedly tapping the big green button and cursing. He's never made it past the fourth pipe, because he gets too excited.
Who presses it? Just Vader. Nobody else plays with Vader's helmet. Ahem.