I see people conclude their presentations all the time by showing a QR code so the audience can later scan and dive into specific information not easily found by searching the internet. Sometimes as simple as contact card, sometimes as involved as a product purchase page, these follow up connections can really enhance the value of your presentation for your audience.
If you're presenting to an audience with an electronic display, consider upping your closing QR code game with an animated QR code.
Rather than the average presenter putting up a blocky QR code, you can catch your audience's attention - and help them out - by having your final QR code animate back and forth to your portrait, or your company's logo or product. Help them know what they're scanning, help assure them that it will scan to what they think it will, and please their eyes with a visual treat at the end.
Your presentation is what they'll be chatting about in the lobby afterward.