Was talking about this in the server and a lot of people seemed to like the idea so:
Rare vendor that has a chance of spawning for a short amount of time. Maybe a 5% chance to spawn every hour on the hour or w/e is balanced.
Have it spawn and walk around for a short bit then de-spawn, or just have it spawn in obscure locations that require players to find it before it despawns.
Let the vendor sell rare items in limited stock with expensive price tags.
Crate drops via vendor basically, give it random inventory (like awps, jihads, jetpacks, etc..) in small amounts of stock (1-5 each item).
Could have it de-spawn after a certain amount of time, or when it runs out of invintory, or both. ;D
Rare item ideas:
Spawn NPC's: Spawn a banker / lawyer / dealer NPC or Item that stays till you disconnect.
Teleporter Pad: Pick a location that you can teleport back to. Balancing would need to be considered. Probably make the teleport take time to happen so you can't insta tele from combat, and have it destroy when you disconnect.