ITT: we post pictures of original, ridiculously overpowered SK guns
Use SpiralSpy for this if you wish to contribute. I'll start.

Eight Slugs. One Slug-colored Callahan. One gigantic Neutralizer. Give me a single reason why this is a bad idea.
http://imgur.com/p18IhON

First off I'd really like a matchmaking system that tries to create balanced teams to ensure closer games (because rolling a bunch of noobs isn't fun, and getting rolled isn't fun).

Class saturation and diversity encouragement: Why not make it so that the class you pick has a shield meter determined by how many other people are playing that class? The more people using that class the smaller your shield bar, teams of just one class or mainly one class would be decimated while balanced teams would have little change.

So the high tier knights don't have much challenge levels when it comes to arcade floors.... how about a new level modifier so powerful it has to be limited only to Stratum 6

Fog levels...

What is this? Basically the entire level (except the area with arsenal station) would be covered in a thin layer of fog that deals minor status.
This would severely limit knights if not outright kill them if their armor is poorly matched, but for those who have a varied armor stash they offer little trouble.

what if there was a bomb type that exploded like a shard bomb but acts like the charge attack of the tortofist. it's meant to catch enemies in the center and then they can't out because it counts as impassable terrain while dealing damage. there should be other variants that cause status effects.

I had an idea, what if we had possible one or two tower defense missions?
Possible one in tier 2 or tier 3 possibly, it could even turn out to an event or daily prestige mission!

Possible scenarios
1: Darkfang assembly line;
Waves of construct and gremlin swarm in from around whatever the players are defending, as the waves get bigger (Possibly around 5 and up) Battlepods will come into the area on some method of transport, and at the very last wave, lesser versions of the roarmulus twins.

2: (Undead);

Curious Mewkat variants, all with the non-aggro faces and an option that sets them to t1-t3 appearances.
Spookat
Pepperkat
Bloogato
Hurkat
Statikat
Black Kat

Zombie Bellhop variants, all with an option to set from t1 to t3
Dust Zombie (blue eyes)
Slag Walker
Frozen Shambler
Droul
Frankenzom
Carnavon

Eight new Guild Hall themes:
Firestorm Citadel
Citadel (Extinguished variant)
Almirian Citadel (Restored, shining, ivory variant)
Jelly Palace
Sky Islands (Day, autumn, night)
Scarlet Fortress

1:
Permanent trinket slot upgrades:

I feel this has to be adressed as Spiral knight is an RPG, and trinkets is an essential part of RPS's. Trinkets is an impotant part of customising your charecter to fitt your playstyle, and to make us pay for it once is fine... But when we have to pay for it over and over and over it just ruins that aspect of the game, and most players don't use them for that reason.
Rather than to charge the prize over and over, please set a higher, but permanent one time prize for each trinket slot.

The weapon slot upgrades are fine as they are. ^^

what if we turned a 360 and made gunners SK's glass cannons and sworders the tanky lineholders
you do the rest

1) Put promo boxes on auction house featured. Place rare boxes in single units with bids only, while the common/less sought boxes go for buy out prices. Starting prices can be adjusted by hand to sway the cr sink size.

2) Re-enable super brawl to bring back some pvp-ers at least temporarily. Maybe make it a temporary event if it's that broken.

3) Make a new achievement hat for tf2. You'll easily get thousands of people average again. I wish I knew the logistics of getting valve to agree to this though.

I have ideas for something.