The Theseus Class Research Vehicle.
It may not be legally obtained, but if I didn't have it, I would probably be dead by now. According to its user manual, its name come from its ability to fabricate its own parts and modular upgrades. It has powered by lucite and has amphibious, walking, and short term flying capabilities. It is designed to be able to house two people in its lower cabin and carry loads of up to 7 tons. The doors to the lower cabin are airtight and have air and water filtration systems designed to sustain researchers on long field missions in Mysteria's unpredictable terrain.
It also has an algea cube generator. (I am so tired of eating that stuff, but at least it's food.)
The Omnitool.
When I first commandeered the Theseus, I didn't realize that this versatile device had been pre-stowed in the lower cabin. I am so grateful for the fact it was however. This thing has saved my life on multiple occasions and I feel like i keep discovering new uses for it every day. It has five main modes that I have disccovered so far: Inactive, Gun, Grapple, Drill, and Aerial. Like all the technology used by the Mysteria Research Team, it is powered by lucite.