Hard pick, but in the end, I decided to go with Whamon. It just always intrigued me, between its immense size (which gets hilariously shrunken down in pretty much every video game appearance), to the fact that it's one of the only Digimon to be retconned into a Perfect.
Though I would like to give shout-outs to SkullGreymon, which seems to be that unloved child of the Greymon family (also, I enjoy that some recent games finally provided it with a more sentient portrayal, despite the profile implying that its brain literally rotted away), and Veggimon, one of the original poop-throwers who somehow managed to break out of that role for the most part (though even if it isn't tossing around fertilizer, it can still be pretty disgusting, depending on whether the media in question decides that its breath should be putrid or sweet).
Garurumon is prob the coolest of the bunch tho that makes me feel normie. Also I just noticed but what's with that Attribute balance of this vpet, not a single Data Champion and other than Vegiemon, the failure, they're all Vaccine.
It is pretty odd that Vaccine is what they decided to go with for nearly all of them, especially when you consider that the original Digital Monster guys had their attributes added retroactively. Granted, by the time Digimon World came out, Kabuterimon was already added to Nature Spirits, I think Whamon was already in Deep Savers, and they MAYBE already had plans to feature Garurumon in Nightmare Spirits (and they must've needed a Vaccine because they were racking their brains over how to make a Pendulum full of literal demons have an evolution chain that appears heroic..... though that doesn't quite explain why Gabumon's Data, with the line flipflopping to Data again for MetalGarurumon). Plans for the anime might've already been in place too, so I could imagine them giving both Piyomon and Birdramon the Vaccine attribute just to add onto the heroic image. [shrugs] Yukidarumon definitely seems like it could've been a Data, though. More so since it's somewhat of a counterpart to Meramon.