Partey.io - Invite to parties and events. Dead simple, privacy-first. Just send a link to your friends. No accounts needed!
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
IveTime - Bored? Meet and find friends spontaneously in one tap!
pretix - pretix helps you to sell tickets for your event in an easy way. It supports multi-lingual events and provides a wide range of features