Affinity Aggro deck packed full of win-conditions. The main goal is to 1: drop your hand early, 2: get 10-16 damage from combat, 3) close things out with burn spells. The deck is really fast at closing out games, which is it's main strength over 8-cast type decks, with the other being it isn't as weak into Orcish Bowmasters. It's the way I like to play affinity, because its most similar to my main deck of burn. This build can run sideboard cards in all 5 colours, and has Urza's Saga to help with maindeck hate cards (also searching a lot of your core engine cards and Welding Jars), and also give the deck some play in a grind game. The main weakness of the deck is that it is pretty vulnerable to Stony Silence and Collector Ouphe, but you do have outs. The main strength of the deck is that it can run the best-of-the-best sideboard cards in all 5 colours, and it will just outpace a lot of decks game 1.
Into the card-by-card.
Mana Base
4x Mox Opal
It isn't technically a land, but in this deck you'll fuel Metalcraft early almost every turn. Being legendary is a pretty big downside, but it still acts like Lotus Petal in multiples, so it's not a huge one. This being back in the format is a huge reason I'm once again interested in Affinity.
4x Darksteel Citadel
Darksteel Citadel fuels your artifact syngergies, without being as weak into artifact, and most importantly comes into play untapped. This card gets worse and worse all of the time, because more and more ways to exile artifacts come into the game, but you'll often have a better target by the time the opponent gets to use artifact removal.
3x Springleaf Drum
Springleaf Drum also really helps with pooping out your hand early, and we're running it over other options because casting it for colourless is still a huge upside. With Memnite and Ornithopter in the deck it will tap for any colour turn 1 reasonably often, and being an artifact helps to turn on Mox Opal.
4x Spire of Industry
This card is run out of fear of Collector Ouphe and Stony Silence, which otherwise would hose the deck hard. There are other artifact lands, and other lands that grant mana in all five colours, but we're trying to find a balance between having outs to hate cards, and mostly running synergies in the mana base.
4x Inkmoth Nexus
This is bad as a land, but very good as a win-con. Turning into an artifact fuels artifact synergies like Cranial Plating and Arcbound Ravager, but mostly this is here as a back-up threat. Being evasive is huge, and with a few ways to pump it in the deck it will close out some games for you in one or two swings. Urza's Saga is slightly better as a win-con than Inkmoth in that construct tokens are more synergystic with the burn spells than Inkmoth is, but Inkmoth is still valuable for attacking along a different axis, allowing you to burn creatures instead of faces.
4x Urza's Saga
Technically an enchantment, but it provides artifact synergies, and serves as both a toolbox card to tutor hate pieces game 1, and a back-up win condition by creating constructs. The best part is, in this deck, Saga searches you mana, win-cons, hate pieces, protection, etc, and for all of that it can be played turn 1 and still poop out a construct turn 2. This land also helps you up your mana count to 24 to mitigate screw, while itself being a mana sink to mitigate flood, so all in all this card actually helps make your mana better too.
1x Mountain
You still want to have a basic in the deck for removal effects that fetch you a basic, and the main deck is almost entirely red, so Mountain it is. Blood Moon, and Magus of the Moon, while still good against your win conditions lands, particularly Saga, shouldn't usually have that much impact on your actual ability to cast cards. Harbinger of the Seas is still pretty good game 1, but games 2 and 3 you run enough blue in the sideboard that you should be able to mitigate this as well, not to mention Opal, Drum, and Mountain giving you 8 outs to still burn their face (or the Harbinger itself, or any other threat).
0 drop creatures
4x Ornithopter, 4x Memnite
These 8 cards give you plety of 0 drop artifact creatures for Drum, Opal, and everything else. Ornithopter doubles as a win-con against decks that aren't in the air, as you can equip it with Cranial Plating to swing for massive evasive damage.
Win-Cons
4x Signal Pest
Since you can put a lot of bodies on the board very early, this gives you a cheap artifact creature to pump the damage out with. Not having haste makes this card much worse, but it's still pretty threatening in a lot of early game boardstates, and is useful with the "go wide" strategies in the deck. The deck does go both wide and tall, which is pretty sweet.
4x Cranial Plating
This is your main win-con, and rewards you for going wide by allowing you to go tall. Being 2 mana to play, colorless to play, 1 mana to equip, makes it still the best version of this kind of effect, and the BB insta equip will still come up in some combat situations.
4x Arcbound Ravager
Yet another tool to turn a "go wide" situation into a "go tall" situation, this card still hasn't been powercrept. It's not as good in this deck as in more token based affinity decks, but it still creates openings to win the game all over the place, and it also works as a repeatable combat trick. Some negative synergy with Construct Tokens and Plating isn't enough to scare me off of packing 4 of these babies.
Burn spells
4x Galvanic Blast, 4x Shrapnel Blast
While these cards do slightly different things, and have slightly different synergies with the deck, they make it so our main deck removal also gives us the reach to close out games faster. I really like running all 8 of these in the main deck, but they're also often the first thing you should be siding out of. Irrelevant Saga cards are technically first, whichever 4 of these seems worse in the matchup, then Welding Jar are the most sided out cards. These cards give you a reason to be mono-red instead of mono-blue.
Saga Package
Technically, a lot of the deck is part of the Saga package. Opal and Drum allow Saga to get mana, Pest and to a lesser degree Ornithopter allow Saga to tutor win-conditions.
3x Welding Jar
A maindeck tool to play through destruction effects, not that useful against white, but otherwise very good against removal. Technically we're trying to draw this card some of the time, but mostly it fits in with the Saga fetchable.
1x Haywire Mite
Mite gives us maindeck, and searchable, artifact and enchantment removal. Technically this is the one non-red card in the deck, but it should be key in giving us outs to hate cards that otherwise hose us insanely well, and usually should stay in games 2-3.
1x Lavaspur Boots
Fetchable with Saga. The haste effect will sometimes allow you to close a game earlier, which the ward effect slightly insulates your main win-conditions against removal. This card also allows Pest to exert immediate pressure.
1x Shadowspear
Lots of equipment in this deck. This one is mostly here to give you some fetchable life gain, but the bonus effect for turning off common protection effects makes this even more fetchable in some board states.
1x Pyrite Spellbomb
This gives us fetchable removal for protection from red effects, and also can be fired off at faces or turn a resolved Saga into a draw, so it seems pretty useful in a lot of situations, and fine to see since at worst it's a cheap artifact that cycles.
1x Tormod's Crypt
Good grave hate is good. Not particularly useful outside of specific matchups, but being a free artifact to power up Opal and other synergies is good enough in game 1, and it enables Saga to always find grave hate.
One thing you might note is that they're no Mishra's Bauble. That's because the card is both a nothingburger, and because we're fast enough that delaying the draw isn't reasonable. Sure, being a free artifact is great, but I'd rather Welding Jar and a Saga package in this type of aggressive affinity.
Sideboard
Saga targets
1x Grafdigger's Cage
This card has a couple of uses. It's often good as grave hate, meaning you have a little bit more and some options. Itt sometimes can't serve that purpose, but its secondary effect shutting off summons from the deck is also something we want the ability to tutor in some matchups, like Creativity.
1x Pithing Needle
Extremely good both to see and tutor against Planeswalkers and other activated effects. This card is extremely flexible, but I don't think you need to main deck it. Bring it in whenever you see a target.
And that's it, most of the saga package is in the main deck.
2x Boseiju, Who Endures
This is our artifact/enchantment removal of choice, mostly because it is also good against Urzatron and Chalice of the Void, but secondarily because you can side out of Mountain or Spire of Industry and still into more artifact/enchantment hate without losing any of your core engine. The other options for this slot either don't apply, or gain the opponent life, which is extremely anti-synergistic with the plan of burning them out.
2x Dispatch
This card give you exile removal for creatures, which could be huge against fatties and graveyard synergies, and metalcraft is such a breeze to turn on that this is a no-brainer over the other options.
2x Spell Pierce, 2x Metallic Rebuke, 1x Mystical Dispute, 1x Veil of Summer
This little, mostly blue, package of countermagic give you some good tools against non-creature combo, or in Counterspell wars, and also allows you to tilt to blue against Harbinger of the Seas, which is a pretty good hoser for the deck and is often a counterspell war/combo.
3x Mindbreak Trap
These are particularly good against Ruby Storm, and basically exclusively here for that matchup. Counterspells can still be good against Storm decks, but Mindbreak Trap is much better since seeing it forces them to back their win with countermagic or basically lose on the spot. Ral makes the previous statement not entirely true, but you have plenty of removal for him, so the matchup is much improved by this one card, which is good, because Storm can actually race you pretty effectively otherwise.
EDIT: Trimmed some cards to make room for Patchwork Automaton. I totally forgot about this card for a little bit, but the ward makes it highly appealing over other win conditions, especially since your other win conditions are good in 2+ card combos mainly, and Patchy is just good on it's own. In addition to trimming on 1 each of three winconditions, I decided to make the deck 7 Blast since the fourth Shrapnel Blast meant that I saw too many of these cards in multiples. I still like the modality of closing out games while being early removal for Ocelots and Monkeys. Pyrite spellbomb gives me the 8th burn spell in some sitations, and the modality of drawing a card and simply being an artifact makes it often better than Shrapnel Blast at removing creatures, particularly since you don't have to sacrifice anything.
