McDonald's employed Snapchat's geofilter technology to tap into Snapchat's 100,000,000 daily users. Of course a marketing campaign on this scale would be extremely expensive, but it's a great demonstration of how companies (big and small) can utilize Snapchat's technology to create a fun and interactive user experience as part of their marketing operations.
This article elaborates on why geofilters are a fantastic and affordable way of building brand recognition.
Let's say 100 Snapchat users attend your company's event and add your geofilter to their Stories. We'll assume that each of those users have 100 Snapchat Friends each. If every single one of the attendees' Snapchat friends views their Snapchat Stories before they expire, your company name will now have been exposed to 10,000 independent Snapchat users.