Someone said it already, but yes...guild...BLIMPS!
I rest my case.
Ok, you want more, allow guild investment in building it, parts needed from all professions, epic parts needing 525 skill, and allow the guild to see it slowly coming together over time.
Once it's complete, all the guild leader to choose a zone and place in that zone to drop anchor, so you can have your blimp, complete with massive guild crest and title on the side, on display for all, and a free gadget for all guildies honoured with the guild, that allows them to 'hearthstone' back to the blimp.
Inside, of course, display cabinets of old epic and legendary weapons and training dummies that can only display a full tier set, giving the crazy types a reason to head back to old raids to farm them. Perhaps some kind of trophy cabinet showing a gift from each faction you're exalted with.
As you pack out your guild blimp, the outside could get larger and even more excessively overexpensive, with gold trim, tassels, jewels, lighting, etc, giving people a reason to make THEIR guild blimp something to shame Xzibit on 'Pimp Mah Blimp'.
Ok, maybe I overthought this one.
Still, who didn't like the alliance and horde war blimps in Icecrown? Who in fact landed on the wrong one like an idiot at least once?