Monarch Deerstalker from MotorStorm: Pacific Rift.
Pacific Rift is an interesting game in the sense that certain vehicle unlocks are tied to trophies. You unlock a specific trophy and earn a specific vehicle. The game's signature Wombat Typhoon for example can only be unlocked by beating all developer ghosts in time attack. It was something different that I liked during its early years, but don't like now that its deplatformed.
The Monarch Deerstalker was an award paired with a trophy for reaching the highest rank in
ranked online. And unlike most online games, whilst coming in a good position earns you progress, coming in the bottom half of the race grid (regardless of player count) loses you progress, and at a seemingly higher rate from personal experience. Now you can just imagine how irritating that would be, especially with the game being well above mere contact racing. And that's not mentioning the big rig griefers.
The deerstalker just wasn't a worthy payout for enduring such a headache. Especially since in that game, ATVs have a bizarre hidden mechanic related to the controller's tilt functionality. If you don't keep the controller straight in your hands, your ATV will flip on a constant basis. And if they start to tip over, you need to tilt the controller in the opposite direction to put them back on their wheels. What's more, they weren't the best performers in any respect. They had decent acceleration but not the best, weren't good for tough terrain, had the lowest top speed in the game, and despite having two extra wheels, were less stable than bikes.
But this is a double-edged sword. I'm both miserable and glad that the Deerstalker is in its position. Because now that the servers are down, it and all other online trophy required vehicles are no longer obtainable. I never unlocked it myself, in fact it was the one vehicle I couldn't get before the servers went down. But if I could choose any vehicle to miss out on, it'd certainly be on my list.