98 hours, spent entirely in Destiny's first level. Holy shit. The dedicated (and ridiculous) player is none other than SerfaBoy, and you can watch him grind his way to level 40 in the video below.
So, how does this even work? Well, normally this mission wants you to get to the end and collect your ship. Except SerfaBoy never does that. Instead, SerfaBoy leaves the game over and over again, and then reloads back in. The game then repopulates itself with enemies, allowing SerfaBoy to accrue more experience every time he pops back into the game. "So long as Rahn lives, the mission never ends," SerfaBoy explains.
Over on Reddit, SerfaBoy gives a more thorough breakdown of how he figured this out, and it's an amusing read. At first, he was worried that the more levels he gained, the less XP enemies would give out -- eventually not giving any out at all. Thankfully, that wasn't the case.
I don't know about you, but this seems like the most Destiny thing ever, too. Players are so hungry for new content, they're willing to just replay the first level over and over again for shits and giggles? Damn.