So I was fooling around with the item rules for Smash Bros. 4 3DS and came across a new idea involving two of the new items introduced to the game; the Beetle and the Boss Galaga (hence the name of the unofficial game mode). The rules are that everyone has only one stock, the only items allowed are the Beetle and Boss Galaga (to guarantee that they appear but you can also include the S-Flag) and I recommend making it an at least 3 player game.
In this game mode you hit your opponents to increase their damage percentages and then use the items to KO your opponents (so if there are CPUs make sure they can't launch others easily at low percentages). Sounds simple, but in execution you get a hectic game that's sure to keep everyone on their toes!
And now I'll share with you a little story on why the third player is recommended: I was playing another round of Boss Beetle to finalize the rules; it's Dark Pit (Me) versus Palutena (CPU) and everything was going well enough when the game decided to spawn nothing but Beetles. I managed to get every Beetle but, honestly, I think the only reason I did was because I was juggling Palutena in the air with the things! It would go like she'd escape the grip of one Beetle only to immediately be caught by the next in an instant! The juggling stopped not because she was finally carried off by a Beetle but it was when the game finally poofed in a Boss Galaga instead of a Beetle. With a CPU, that's hilarious! With a human player, that's trolling (some would argue that'd make it even more hilarious). The third player is there to make a scenario like this harder to execute and cut down on frustration… But you're free to go 1-on-1 with a CPU and do this to them. I endorse CPU abuse.