Swag is always good. Stickers are a given. One conference I attended had a company handing out cards with a puzzle on it (encoded message). Decode the message

Swag is always good. Stickers are a given. One conference I attended had a company handing out cards with a puzzle on it (encoded message). Decode the message and email it to them and they tell you to drop by their booth for a free t-shirt. Clever way of collecting email addresses for recruiting and they mention that they're hiring when you get the shirt. They never did spam me via email, so I didn't think it was too intrusive.