Group projects.
I'm doing a graphic design and storytelling project, and I foolishly allowed someone else to become involved, and he's making it impossible to move forward. I genuinely like the guy, and his work is good, but he's so detail-oriented and has so little time to devote to the project that it takes him forever to do anything. Before he joined, I had been working on the project for 10 months, and had moved through 19 years of story. In the 5 months after he joined, we moved forward 7 years. That's not as fast as I would like, but it's tolerable. In the past 3 months, we've moved basically 1 year. I confronted him about it over a month ago (I told him that we needed to get moving, and asked if there was anything that I could do to help). He apologized, and said that he would move forward within the week. Instead, he launched into a massive side story, then stopped halfway through. He hasn't posted anything in over 2 weeks.
I'm thinking that I just have to offer an ultimatum: I'm posting the next year on Friday. If you're caught up, that's cool, if you're not, that's too bad, but you've left me unable to do anything for months. If you don't have time to do this, you don't have time to do it, which is fine, but I can't let you hold me up anymore.