Deck choice
Jund was in my mind from the start, for the obvious reasons. It's been my favourite Modern deck since I started watching the format, it has delicious GB grindiness, and it has a nice toolbox. I'm pretty sure everyone anticipated this, especially after I called out Jund as my favourite Modern deck in my post-Legacy write-up and, y'know, said people risked the mirror with me if they picked Jund - even if I hadn't settled on my deck at the time.
That said, it was kind of predictable and it's not like I don't have other pet decks. I probably ran through more KCI games than Jund in the lead-up to this, because it's interesting and fun as an exercise. But that's just playing solitaire, so not happening for a friendly tournament. Similarly, Deadguy Ale, while there's lots of interaction on my part, through discard and land-killing, would have been too unfun for other people. I also considered favoured child Mono-Green Stompy, but discarded it as too linear - there's play to it, but 90% of matches would have been decided one way or another by T4 and, again, that seemed sort of a sad thing to present people with. (Though it's more fun to play against than KCI or Deadguy, so I'm not totally ruling it out in future). My Mardu control deck just didn't feel in shape for the tournament - I wasn't averse to playing a low-tier deck (into which category Mono-Green Stompy definitively falls, and neither KCI nor Deadguy are exactly T1) but there's a difference between playing a non-competitive deck and a bad deck.
So, as I mentioned to a couple of people, I decided to just go for it and be the Jund player that I am. The comment that I was going to get hated out was made after I'd decided that; it was a bit of mindgames, but also the fact that it was blatantly obvious what I was going to play, especially having hinted at it in the thread. Jund may be renowned for having no worse than 50% matchups against everything, but there are (good) decks that turn the screws on it really badly if you want them. GR Tron pre-Eye banning was well-known for it; Eldrazi is horrible; and Siriel's spoiler deck is also a terrible match-up that I had no right to win. (Conversely, I also benefited from some great match-ups and opponent draws: Lyco quickly pulled Allosaurus Rider both games, and while he's got to go for it by all means, that's still really asking for Jund to three-for-one you, besides making hand attack a lot easier on my end too).
Deck Tech
As I revealed to some people, this is a minimally changed list which I'd had since about January of this year, I think. It's not hyper-tuned to this tournament (which I suppose is good because I didn't really guess the meta well) so lots of comments are just about what (I think) I was anticipating at the time.
I don't like your stuff: discard it
4 Inquisition of Kozilek
2 Thoughtseize
4/2 split even though there are a fair number of relevant 4+ drops in Modern, because this deck can really run through its life total, especially if you're as aggressive about shocklands as I am.
I don't like your stuff: kill it
4 Lightning Bolt
3 Abrupt Decay
2 Terminate
1 Dreadbore
1 Maelstrom Pulse
Lightning Bolt at 4x for its enormous versatility and usefulness. Then opted for a relatively broad mix of answers, which is the way I personally like it. (I retained a single Dreadbore where Nil left it out, for example, but it's also less important that I act at instant speed than it is for his deck; in fact, I'm often casting instants on my turn just to reduce the likelihood they'll be countered or otherwise responded to). Left toughness-killers to the bolts, on the grounds that I was seeing lots of Tasigurs and Eldrazi at the time, IIRC: if these can hit something, it should die.
I don't like your stuff: discard it AND kill it
4 Liliana of Veil
2 Kolaghan's Command
4x Liliana because her power as an attrition card is key to the whole way Jund operates. K-Command is really nice, and I remember trying to fit in another during deck construction, but it's honestly a tad expensive. I often want to be casting multiple spells a turn, either for punishing early games, or taking advantage of having ground the opponent out later, and 3 mana makes that more difficult.
I like my stuff: get more of it
4 Dark Confidant
The full four is probably necessary in this list (and most Jund lists, of course), since I'm not supplementing them with anything like Painful Truths, but they do hurt. Especially in more creature-based metas, they can be pretty ineffective on the ground, particularly compared to the days when a 2/1 in Modern could expect to take 6-10 points out of an opponent's life total.
I don't like your face: smash it
4 Tarmogoyf
Duh. Kept it simple instead of opting for any of the delve creatures as supplement.
These guys don't like your face either, and also hate your stuff so much they get better when it dies
2 Kalitas, Traitor of Ghet
3 Scavenging Ooze
A wondrously main-deckable power package that means I don't have to have masses of dedicated grave hate in the side.
Kalitas is the latest answer to Jund's problem of what it should put in its four-drop slot since BBE went. Reid Duke had been having a fair bit of success with them in his decks around the time I made this, so I opted to try it out. Pretty impressed overall, despite having to cut down my favoured Huntmaster value machines to fit them in. Kalitas' lifelink (which is relatively easy to overlook compared to the rest of his text) and the lifegain from Scooze were both relevant a reasonable number of times, again saving me and my deck from our reckless life use. If these two worked better together, it would be close to perfect, but you can't have everything.
My lands don't even like your face (Have you noticed Jund is a very angry plane yet?)
3 Raging Ravine
1 Treetop Village
Three Ravines because an on-demand 4/4 attacker is gorgeous and the fixing is much appreciated, especially as it lets me concentrate more on the important black lands in the rest of my mana base. A token Treetop for situations where the horribly expensive activation cost of Ravine is preventing me from doing things. Manlands in general are really important for Jund, because this is an attrition deck far more than a value deck. (This is an important distinction which people picking up Jund from just its reputation commonly fail to apprehend). You much more frequently trade cards with your discard or your removal than get two-for-ones; Lili's discard is symmetrical; none of your beaters are especially resilient beyond their (potentially, eventually) high toughness. It's very easy to end up with both players having empty hands and no creatures, at which point being able to tear someone's face off with a land is a key route to victory.
(Slightly) less angry lands
2 Stomping Ground
2 Overgrown Tomb
1 Blood Crypt
3 Blackcleave Cliffs
2 Bloodstained Mire
4 Verdant Catacombs
2 Wooded Foothills
1 Twilight Mire
1 Forest
2 Swamp
Black's really important in this deck, so a lot of the fixing is dedicated just to that, and all the fastlands are the R/B ones for that purpose. Especially early, you also want access to Red for Bolt; later, green comes up in importance once you're casting your 'Goyfs and activating manlands. Looking at this list, I'm certain I should change a Stomping Ground for another Blood Crypt, in fact. (A relic of me previously playing Huntmaster over Kalitas, perhaps?) Advantages of being forced to re-consider your deck card-by-card!
The stuff that hates you and your stuff so much it has to be kept in a special pen and not used until after the first game has finished
SB: 1 Pithing Needle
SB: 2 Grafdigger's Cage
SB: 2 Fulminator Mage
SB: 2 Duress
SB: 2 Pyroclasm
SB: 3 Ancient Grudge
SB: 1 Chandra, Pyromaster
SB: 1 Kitchen Finks
SB: 1 Thrun, the Last Troll
The various answers in their relatively obvious places: Finks stalls burn and all-in aggro, Pyroclasm wipes hordes of small creatures, Fulminators deal with land shennanigans; Grudges hate on artifacts; Thrun smashes up control decks stuffed with removal.
Cage deals with graveyard stuff of course, but there is a second often-overlooked part to it too, perhaps thanks to the card's flavour. And stopping creatures entering from the library is getting more and more relevant in Modern. No Collected Company, no Eldritch Evolution, no Nahiri ults ...
Duress is particularly there for the Burn matchup, which is why it isn't extra copies of the more versatile Thoughtseize. Nevertheless, it's still decent at disrupting control and combo.
Chandra is very much there for the grindy match-ups, even if I did bring her in against aldeayeah to ping his little creatures. (I had reasonable confidence I'd be able to keep him from going off too quickly at least by G2). A couple of times during this tournament I had Chandra 0-ing safely with a Confidant on the board, and drawing three cards a turn for free felt pretty glorious tbh.
Changes for the tournament
I put in an extra land just as a matter of tuning, and that served me well on a couple of occasions where I took risky one-land keeps. Cut my final Huntmaster for it, cementing Kalitas' dominance.
Put in another sideboard Grudge for a Feed the Clan, since Burn had died down a bit from when I'd built this and I wasn't really putting anyone on Burn. I was anticipating at least one person playing an artifact-heavy deck - some kind of combo if not Affinity - and thought that at worst I could probably clear out some hateful artifacts that would be brought in from sideboards. As it turns out, with spoiler in the tournament and no artifacts presenting themselves to me whatsoever, the Feed the Clan would actually have been better.
That's it. I said I didn't do much.