[Edit: added a couple of screenshots]

Many people have told me that they'd like to participate in the 4k Challenge, but haven't any ideas on what they should make--I've the exact opposite problem: I have far too many ideas that I'd enjoy attempting. However, knowing full well that should I post any of these ideas in detail, I am 100% guaranteed to lose all motivation for the projects, I've decided to help the poor by posting some of the ideas I'd like to rule out for myself. Feel free to pick one of them up and win.

1. Mowing/Racing game
A half-decent name for this game would be something like "Need for Seed: Underground" or, if you can get the sponsorship, "Ford's Mow 'er Short." I wouldn't attempt this game without a much better title, but the potential possibilities here are nigh unto endless. I'm sure I'm not the only one who's ever dreamed of pimping out a riding lawnmower with spoilers, hydraulics, spinners, and even NOS. Here's a game where players could race on a course, or compete on identical patches of grass to see who can complete their yard first, without having the neighbor lady bitch about today's lazy-ass generation and their slipshod mowing abilities. The money earned mowing could be spent on new rigs, and players would be constantly pushing to add that extra inch to the cutting diameter. They could go bagged or even incinerator; riding lawnmowers offer so many unique parts to trick out--not just the blades, but the blade carriage and...the seat. You could even design a trick mode where players take their mowers off some sweet jumps and attempt insane moves like "no-handed can can" or "double, no, triple superman flair 540." I'd personally spend most of the time engaging the blades, bailing, and trying to get the mower to land on something cool. Come to think of it, you could probably do a destruction derby mode where you remove the safety decks and have open blades.

Big Blue tops out at 30, drafting off of his competitor in this dragmowing event--check out that underglow!.

2. Porn Site Tycoon
I'll bet somebody's already made this somewhere on the internet, and it's only a matter of time before we see this in-stores as the latest installment of a certain franchise, but I was somewhat...vaguely...just remotely considering it myself. It'd be relatively easy to construct; you'd just use the statpanel to track stats like "subscribers," "cash," and "stars" and ask players to tweak values like "monthly fee," "free trial period," and "employee pay." Players would use the money to work their way through college, purchase new software like "DreamWeaver" or "Photoshop" (to touch up on their "celebrity" sections), hire artists, and pay their stars; you might even give them the option to go voyeur and save money in that last department. You could do a Madlib style article generator to save space, and you'd probably have more than enough bytes remaining to generate random, variously-sized pics using 8x8 pixel blocks in a variety of shades from dark chocolate to near vanilla to give them that "censored" look.

3. Fangame simulator: DBZ 4Eva!
You're welcome to choose any fangame genre you like--or dislike, as the case may be--, but I'll be using DragonballZ in my example. In this game, players would attempt to goad their simulated fanbase into playing their ripped game over everyone else's, eventually aiming to climb to the top of the nonexistent Byond.All_DBZ_Only channel. They can play an "open source" mode in which they name the game and copy/paste code snippets from a list of 20-30 commonly used player hooks like "pets" and "aging" to make their game unique, or they could play "classic scenario" mode by choosing one of the 5,862,743 greatest DBZ games in BYOND history. The best thing about a fangame simulator is that one set of code and icons applies equally well and looks just as original in every game players simulate! If the digital players complain too much about ripping, just add entrance alerts to make sure they know about the things that really give a DBZ fangame its character--things like its positive oldbies, its gracious hosts, its lenient and forgiving GMs, and the pure creative genius of its creator. To prove that you're completely against ripping, throw in a few threats about stealing your copyrighted material, and also be sure to point out that your 236 GMs were exlusively hand-picked and other would-bes need not apply.

Simulated player, xSsJxGoKuX69, enjoys the complex and incredibly flexible training system of what might be either "DragonballZ: Euthenasia," "DragonballZ: Conflageration," or "DragonballZ: Apocalyptic Plague."

I've got quite a few more ideas in mind; if all of these get taken, or none of them tickle your fancy, I may post some more. I might also whip up and post some screenshots for these...
Man thoes are awesome! If 4k wasn't 1 or 2 days away, I think I would have so much fun doing the porn site tycoon or the dbz-4-eva game. XD oh time..where hast thou gone?
The deadline is JULY 21st, not June. =)
I wouldn't have bothered posting if there was really so little time remaining, Inu. Go ahead and attempt =)
Oh! I will then. =D
Ahaha that is the best ever xD Need for Speed: Lawnmower! And that screenshot is great! You have to much spare time Raven :O Which you shouldn't! Get back to work on Dream Forge! Remember, I still have to assainate you in game, then steal your underwear and sell it on DreamForge E-bay!
Looking forward to porn site tycoon lol!
Mower/Racing one, and great turf work.