The Adventures Of Harry Potter, the Video Game: Exploited, linkffn(9708318), is the most hilarious HP fanfic I've ever read, easily topping the Seventh Horcrux. Unfortunately, it's incomplete.
Here is how the story begins: *Standing in the clearing in the middle of the Forbidden Forest, Death Eaters gathered about, and Voldemort's killing curse flying right for Harry's noggin, Harry closed his eyes and hoped for the best.
The curse hit, and Harry's world went black.
That is, until the giant green glowing letters of GAME OVER flashed in front of him as if on a giant movie screen.
And to add insult to injury, a poorly programmed 8bit computer graphic of a destroyed Hogwarts castle was illuminated by lightning flashing in the background as flocks of pixilated ravens circled the crumbling ruins of the place Harry had called home. And all that time, the words GAME OVER continued to dominate the middle of Harry's awareness.
Harry found himself standing at the base of what appeared to be a movie screen, or a large flat version of the Hogwart's ceiling, but with the words GAME OVER displayed in front of him where now additional words began to be portrayed in front of his quickly paling complexion.  "GAME OVER, sorry, it appears you did not save your game, would you like to start a new game?" Read the words on the screen.
Harry was completely flummoxed. Gobsmacked.
Speechless – for all of fifteen minutes, and then Harry let loose a string of expletives so foul that they would have singed Hagrid's hairy ears and even caused the Dark Lord Voldemort to cry out "Language!"*
Later Harry found his first decent weapon: *Upon picking up the small hand shovel, a chorus of trumpets sounded and a word bubble popped up in Harry's vision, just as the shovel grew in length to be a full dirt shovel longer than Harry was tall and painted in yellow and black spirals up the handle and checkered across the shovels head/blade.
"Tada! With hard labor and diligent work, you've earned the "Hufflepuff Harry" title and a new tool and weapon, the Hufflepuff Shovel. For when there is shit to be done, we know you'll be there diligently shoveling it!"
Harry looked rather nonplussed by his new weapon/tool. "Hardy har har, you're a regular laugh riot is what you are." Harry groused as he looked over his shovel.
"Inventory," Harry called, getting ready to put away his new weapon, only to find a new tab in his inventory called "Weapons." Touching the tab, an expanded area of the chest opened up like closet or armory; though it was rather bare armory with only one Pointy Stick resting on a weapons rack. Still, the addition of the Weapons armory gave Harry some new information he hadn't had before as floating above the Pointy Stick on its rack was the weapons Statistics of: 1 melee attack/1 defense. As Harry set down the shovel in a weapon rack, its statistics floated above it: 3 melee attack/1 defense, Plus 2 to Herbology when wielding Hufflepuff Shovel and Plus 1 to attempts to Hide Bodies or turn them into fertilizer.
Harry paled at the last two details, "I'm never going to look badly at Hufflepuffs again." Harry stated definitively.
Closing his inventory and shaking off the shivers that came from imaging Madame Sprout and how she made her fertilizer, Harry looked around at all the collecting he had done and realized he was done with that for now.*
Harry won his first combat: *Harry was bouncing down the street towards the Dursleys, coming from the direction towards Ms. Figg's house, when he saw two young teenagers in leather jackets poking at a burlap sack that was shaking with loud hissing and cat's meows. An exclamation point hovering over the laughing teens' heads told Harry that this was the mission "The Kneazles In The Bag."
The two teens didn't know what hit them.
Falling upon them like a Bouncing Kindergartner of Doom, four year old Harry Potter used his new 9 points of DuelWielding to bring down the hammer... or at least the Hufflepuff Shovel and Pointy Stick.
"You gain initiative! Surprise attack!"
"Kong!" Harry's Hufflepuff Shovel made a ringing sound as the flat black and yellow checkered metal head of the shovel knocked the teen holding the bag right upside the teen's head. A green bar appeared above the teen's head and immediately dropped into the red, showing the boy's health drop to 2/10 points due to the power of Harry's special weapon; it would also be good for hiding the bodies later.
Meanwhile, using his Pointy Stick like a lance, Harry channeled his rage at getting beaten up by old lady librarians to stab the second boy.
"Critical Hit! Spleen Skewer!" Rang over the second teen's head. The blow immediately dropped the second teenager to 1 health, take bleeding damage that would kill the teen if not healed, and caused the teen to drop to the ground and start screaming, "My Spleen! You stabbed me in the spleen! Why God? Why?"
Due to Harry's attack initiative given his unusually high Dexterity of 4 and lucky surprise attack bonus of a Bouncing Attack From Above, Harry was able to swing his shovel again, braining the first boy and dropping him to 0 health.
In another lifetime, a 4 year old Harry would have been no match for the two boys. In another lifetime where a malnourished 4 year old Harry Potter hadn't ground skills, bunny hopped for hours to increase his stamina and strength stats, and would have only had a Pointy Stick. Well, that Harry would never have had the option of a surprise attack, and that Harry would have gotten his ass kicked and would be learning about how to reload at the last saved game.
This Harry, working off of a Surprise attack and getting to attack twice in a row quickly finished off the two young teenagers.
"Tada! You've defeated Level 2 Weak Teen Hooligans, 250 Experience earned. Loot bodies? Yes, No?"*