[cerious]

Possibly the most fun I've ever had in a long, long time. Mad props.

I don't see how 1-up can work in arena maps. Blue shell should damage the top scorer by 30 health. Traffic cone shouldn't show up on the receiver's screen (it gets in the way and is annoying) and should appear purely cosmetic - i.e., other people see the huge cone, but it doesn't get in the wearer's vision.

And one bug: In arena mode, if you get Running Shoes and the next round starts, you can actually run around in the setup area - on maps like Arena_Harvest_v2, this means you can run around the entire map during the initial 10-second setup.

Also, my own ideas:

Banana Peel.
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It makes you slide around as if you were on ice (this effect is possible in TF2, I've seen maps with this effect) for a few seconds.

Disco Party
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Makes the receiver flash all sorts of colors for 10 seconds - he turns red, blue, green, yellow, etc. and starts flashing colors (not too fast, but not too slow).

Congratulations!
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Purely cosmetic. It renders the little fireworks display that goes off when you earn an achievement. Maybe it refills your ammo supply too.