Stickler will work alongside the managing director, Laura Gregory, and will produce for the directing duo Daddy.
Gregory said: "We've always taken pride in the production back-up at Great Guns and the experience Geoff brings to the group of producers will give us greater insight into the production process from both sides of the fence."
Stickler has spent the past 18 months working as a freelance producer. Before that he launched the TV production arm of Dare Digital, the digital and creative agency founded by the former joint managing director of Bartle Bogle Hegarty, Mark Collier.
Meanwhile, Terry Wordingham, Great Guns' executive producer, is leaving with a view to setting up on his own. He will continue to produce commercials for the features director David Lynch on a freelance basis.
Other changes at the company include the hiring of new directors including Eden Diebel, from Rose Hackney Barber, and Stefan Lindfors, a Finnish designer.