Ah, the humble tilde button, so useless. Unless, that is, you're playing a Bethesda game built on a variation of the Creation Engine. In that case the humble tilde key unlocks the console, a gateway that lets you mess with the game logic. Give yourself superpowers, spawn weapons and monsters, speed up time and complete the game with one tap of the Enter key.
Simply activate the console in-game, type the command you want, press enter and then close the console again and watch your command take effect. If the tilde button (left of the 1 key) doesn't work, try the apostrophe key. It seems to vary depending on the nationality of your keyboard settings.
tgm — Good old god mode.
tcl — No collision. Walk through walls. Walk into the sky. Be free.
tai — Turns AI off and causes everyone to stand still with a vacant look on their face.
tcai — Turns combat AI off. Brings peace to the world. Boring, boring peace.
killall — Kills everyone in the vicinity, apart from companions and any other characters deemed too vital to die. In that case they will slump down injured until you give them a stimpack.
kill [insert ID] — Kills the creature with the ID you supply. Type kill (0017fda3) now and wherever they are, the feral ghoul I tested this on will drop dead.
resurrect [insert ID] — Brings the creature with the ID you supply back to life. Type resurrect (0017fda3) to bring the feral ghoul I tested this on back to life! He's having a torrid day.
setgs fJumpHeightMin [insert number here] — Modifies your jump. Set it really high to vault over buildings like the Incredible Hulk. Warning, if you don't turn on god mode, the falling damage from your own jump will kill you.
speedmult [insert number here] — The number you type in adds multiplier to your running speed, with hilarious consequences. Use in combination with god mode and the next command to go full superhero.
tfc — Activates flycam. This and the next command are great if you want to get good screenshots.
tm — Toggles menus and UI on and off. It even stops you from seeing the console, so you'll have to press tilde and type tm again blind to get the UI back.
setscale [number from 1 to 10] — Makes you or your target HUGE. See the results in the picture at the top of the article.
sexchange — You'll never guess.
player/additem 0000000f [insert number here] — Adds bottlecaps equal to the number you specify.
player/additem 0000000a [insert number here] — Adds bobbypins equal to the number you specify.
player.additem [insert item ID here] [insert number here] — You may have noticed a pattern in the last two commands. Yes, you can add ANY item to your inventory this way as long as you know the item ID. The next command can help you find item IDs.
coc qasmoke — This teleports you to a room with a number of boxes that contain every single item in the game. Surreal, but a good way to find item IDs. You can find an item ID by entering the console and clicking on the item in the game world with your mouse. It turns out that Dogmeat's real name is 0001d162. Alternatively, community wikis will have listed every item ID within a few days.
set timescale to [insert number here] — Speeds up or slows down time. The default setting is 16. 1 is realtime, 10,000 is crazy spectacular timelapse. Be sure to look when time's on fast forward because the sun and the moon actually bounce across the sky.
tdetect — The AI won't detect you anymore. Steal to your heart's content.
[skill] [number] — Boost a skill by a numerical amount of your choosing. Eg. strength 10 will boost your strength by ten points. If there's a terminal you'd love to hack or an NPC you'd love to persuade, use this.
player.setlevel [insert number] — Boost your level to the number specified.
caqs — This completes every step of the primary quest, effectively completing the game for you.WARNING: it if you want to avoid spoiling the entire game for yourself.
There are bound to be lots more that the community will uncover in the coming weeks. We'll keep our eyes open and update this list with the good ones.