My favorite is the endless losing one. First, give an opponent control of a Lich's Mirror. This artifact, if you were to lose, instead resets you to 20 life, shuffle all cards you own into your library, and draw seven.
Then get out anything that prevents life gain.
Then drop your opponent below 0 life. (The hard part!) The loss is prevented by the mirror. But as YOU own the Mirror, it stays out and they do not reset to 20 life due to preventing life gain.
So they lose again. And again. And again. Technically this is a draw as the loop hangs the game. But it sends a message.
I once built, on the old Cockatrice deck emulator, a deck where the idea was to generate infinite mana using the Myr Galvaniser - Palladium Myr combo, then spend that to Genesis Wave for infinity, putting all the permanents in my entire deck onto the field.
Apart from the above myr, the deck would also contain Laboratory Maniac, plus a bunch of stuff with ETB draw triggers.
My favourite infinite combo is currently Warp World, combined with a lot of permanents that increase my permanent count, such as Wood Elves, Hunted Troll (back when the tokens it made were still owned by you), and Saproling Burst. Combined with Anarchist and Eternal Witness you can get the combo off infinitely many times, and increase your permanent count at each iteration (on average). At that point, it's pick your kill mechanism!
A friend was looking at building a Judith Commander deck with Goblin Sharpshooter as his win condition (he loves the artwork for it) and we came up with the following;
Zulaport Cutthroat (or similar flavour) in play, Goblin Sharpshooter with Splinter Twin cast on it.
Tap Goblin Sharpshooter creating a copy of itself with Haste, tap the copy, targeting itself and removing itself from play, triggering Zulaport and pinging an opponent for one. The original Goblin Sharpshooter also untaps because of the creature death trigger.
He ended up not putting it in as a potential Turn 4 kill in a relatively casual meta seemed a little too extreme, but it did cause some hilarity that a card picked because of the artwork was capable of such degeneracy.
A buddy of mine used the Goblin Sharpshooter in combination with the green enchantment that turns all lands into 1/1 creatures (can't remember the name), needless to say, he was the only one left at the table of 6 people with any land. Brutal.
Brago is one of those Commanders that when I see him brought out I go from thinking "This will be a fun game" to "Okay, I'm just going to bring out the most hateful thing I've got with me and screw it". I've never seen a Brago deck that just isn't a souless experience to play.
Gravecrawler / Phyrexian Alter is a classic with another zombie in play. You can sprinkle it with whatever you want as your win condition.
At least with Roon and Aminatou there's some inherent limits, and Aminatou has more than just blink as a viable build path. My Aminatou deck just uses the blinking for occasional value (i.e., pairing with Dreams of the Dead to get around the drawback of Dreams of the Dead) and focuses on library manipulation.
Brago is just saying "I intend to abuse ALL of the triggers".