Honestly I've been getting the feeling that there need to be more colliseum games because all that there is, is a very intense version of bomber man and a map control game. I'm thinking of one in similar to the hunger games and one similar to....... well don't hate me for this but here it is........ Minecraft style survival (these are just Ideas and You could give better ones i beleive.
NO HATERS ALLOWED! AND MOST OF ALL AND GIVE CONSTRUCTIVE!!!!!!!! CRITISISMS
Someone already brought up the 'Hunger Games style' one I believe, and by that, I assume you mean all-on-all fragfest with the last man standing as the winner.
If that was what you had in mind, sorry, no. It happened once, and was called Superbrawl. Dude with the biggest GF won, other's pretty much didn't stand a chance.
If it were to happen, it'd need serious balancing, specifically a damage reduction. Players will die just so quickly, all you'd need is a GF and movement speed increase to get anything done.
Minecraft style? That's a new one, but also no. I don't believe SK can actually support something like that. Also, Minecraft has no scoring system, or even a technical end. Reaching endgame's pretty much it, but there's loads of stuff left undone, even by then. So there really is no end. SK would need a complete redo of most of it's mechanics to cater to such a request, which I at least would find amusing but not worth much in actual playing, considering various possible playstyle mechanics.
"NO HATERS ALLOWED! AND MOST OF ALL AND GIVE CONSTRUCTIVE!!!!!!!! CRITISISMS"
That wasn't necessary; haters only come of their own accord when someone's suggesting something utterly ridiculous or is sounding like such an idiot the suggestion can't be taken seriously.
In fact, in just saying so, you've probably just annoyed the people you wanted to keep out, so now you have a better chance of them kicking down your door and screaming in your face.
"You could give better ones i beleive."
Unfortunately, not many come to mind, except for a possible Capture the Flag mode, which I have only just realized would have a big problem: Almost everyone's walking speed is the same, weapons have limited range, so chasing down the flag bearer is going to be harder than getting away with the flag.
A more plausible idea is a 'Storm the Fort' mode, which I have only just conceived. Pretty much, defenders, attackers. Defenders defend Checkpoints in a fortress, attacks have to destroy the checkpoints. Defenders have to hold out until the time is up, Attackers just have to destroy the final Checkpoint.
Not very detailed, because as I said, I literally just thought of it.