Specifically the Glow in the Dark Digital Monster Ver. 20th. It contains all five of the main Digital Monster line DigiEggs which can hatch into the respective Digimon associated with said Digivice version, and some of which can now achieve Mega Level with some in particular being able to DigiFuse into an even stronger Digimon. This Digivice was also the debut appearance of BlitzGreymon, CresGarurumon, and Omegamon Alter-S in the whole franchise, with me having aimed to acquire both Digimon to DigiFuse into the latter as I was beginning to learn the ropes with how to best acquire the individual forms of whatever Digimon I needed to go into the Digivolution paths for BlitzGreymon and CresGarurumon specifically.
It was quite an acid trip with CresGarurumon, as the easiest route I wound up going for was Elecmon and Whamon as the Rookie and Champion respectively, with the only choice in Ultimate being MetalMamemon. Even if you had went with the harder to accomplish Gabumon and Garurumon, you'd still go into MetalMamemon in-order to get to CresGarurumon. I had an easier time with BlitzGreymon, meanwhile, as the requirements of Greymon were stupidly easy for me to meet which meant I pretty much just had to do battles for both Digimon to have them achieve Ultimate Level before they would later hit Mega Level. Thankfully the Ver. 20th rectifies at least two issues with the older models it's based upon. First is that the save file on the Digivice is not tied to the battery, meaning you can have the same save file kept intact spanning multiple battery replacements. Second is the fact there is an option to battle opponents in a single player session, as I don't believe the original Digital Monster Digivices had such an option.
Also I find it absolutely ironic with the Digivice I got regarding its exclusive Digimon which I will more than likely never get a hold of because of how you unlock it. Each Digivice in the Digital Monster Ver. 20th line has an exclusive DigiEgg you can unlock by communicating with at least 5 other unique Digivices, and it depends heavily on the color of the Digivice which Digimon you get from this. The Digimon I get with my Glow in the Dark model is ironically a Digimon I rather heavily detest; Meicoomon, which had first appeared in Digimon Adventure Tri.
