I am the ultimate offender in this. I talk to every... damned... NPC. I collect every collectable, I have extra of every item in my inventory even if I only need one (in Xenogears I'm hording items. I kept an extra dog-ford from Kislev), I do every quest, I hoard ammo like I'm facing an apocalypse filled with redneck gunmen, and I max out every character I'm presented with. I also keep all my old equipment. I never sell it. I must have at least one of everything I can at the end of the game. :P

I'm actually amusing my mom to great lengths at the moment. We're playing DW6 right now, and for anyone who hasn't played it, you have skill maps for learning your abilities. These skill maps usually offer multiple paths to one skill. Oh god. I must fill in every skill, even if following one straight path is quicker and easier. I can't leave little incomplete paths.