Backstory: From attending recent events, we have a lot of swag; excess usb's, pens galore and tons of random sized sticky notes. Most end up in the corner and thrown out eventually, we'd happily donate them we just don't know where to send them.
The Idea: A swag donation collection company that routinely visits small companies to collect unused swag items.
Deep Dive: You could start by cold calling startup and small companies to see if they have any excess supplies and swag items that they no longer need. You would donate and deliver a receipt back to the company or sell the items and use the money as a donation to a specified charity.
You could also target physical product companies that may have excess stock items like loot crate... I hear they have a lot of excess items laying around ($20M in inventory to be exact).
Validation: Our stuff is collecting dust... someone can definitely use it. Read that loot crate article ^^
Monetization: If you resold the items, you would take a percentage and if you were just donating the items, you would charge a small fee.