This is a copy of an idea I sent to the event team a long time ago that never got used, I still like the idea so I am sharing it again, also I spent too long writing it so I don't want it to die just yet.
Event Name: Community gathering (better name needed)
Details about the event:
A twist on a previously attempted event, core idea being similar to the ore trader event that happened last year, the twist being a number of different items needed to be gathered and a community based prize, bonus exp being the easiest thing to think of. I assume the best way to set it up would be by using an account to set up grand exchange offers of various amounts, and whatever community prize being awarded when however many offers of these are filled. It will require staff to help out ironmen who wish to contribute, and a better understanding of what items are floating about in peoples banks so orders don't get filled instantly, but I see potential. Depending on items chosen you can do a number of things, encourage use of deadish content, adjust ge average on obscure items, or just encourage people to all skill together grinding out a goal, make people fish at catherby shore for raw lobster or something, it is good exp and I doubt many people have 10k laying around to dump in an offer. Additional thought if bonus exp is chosen and cleared by Matt, depending on the size of offers you can make it somewhat of a race, by making the bonus exp prize last for whatever is left of the weekend as extra incentive to grind harder.
A couple of item suggestions for the gathering thing if you need them. Mystic Hat (Light): An uncommon drop from Basilisks, no one really cares about them besides it being a decent alch so I doubt there is a stockpile in someones bank. More importantly though Basilisks drop Jaws, an item people do care about, if you want more faceguards and herbs about its not a terrible idea. Adamant Boots / Mystic Robe Top (Dark): Uncommon drops from Gargoyles, same idea as Basilisks, but Gargoyles offer decent amounts of steel and mithril bars instead. Steam Runes: Everyone must suffer as I have, though they are decent exp, and not dropped by much so I doubt there are large numbers about. They are also rather useful for Chambers of Xeric so people learning how to make them isn't awful. Raw Lobster: Good exp even when banking, you'll just need to check if people have some stockpiled already. Willow logs: Not great exp but they also aren't dropped by anything in game as far as I am aware, also good to recreate 2008 draynor village woodcutting lvl questions. Onyx bolt tips: A higher requirement idea, obtainable in a few different ways including fishing, though a fire cape is required for that. I'd also be worried about there being too many in peoples bank they don't realise they have stockpiled. Ancient Emblem: The most common rare drop from Revenants, if the community would work together to get them or if it'd be a pvp clusterfuck I have no idea.
Additional random thoughts, doing this via the GE allows people to check on the progress very easily and without a staff member constantly updating a thread, though comes with the potential drawback of people trolling with higher buy offers. As for the money to put the offers up in the first place, asking some of the richer players might not be a bad idea, I have seen interest in donating towards a well of goodwill, the idea is similar but with work involved. Can also use the items obtained towards giveaways or as a money sink.