All of the following are if I couldn't get a good friend to talk to, to spend time with. When I was still a student I'd kill time between classes by sitting on a bench, lighting up, and observe people. On days with no classes (and no other project to be done), I'd smoke up at my home and play video games. If I feel being productive, I'll either practice playing guitar, or continue some obscure side project (that will never be done).
All things considered, I'd go to an isolated coffee shop and write (Yes, I'm one of those guys). As of late, my primary time killers are either watching movies, or just plain surfing the web.
All my time is spare. I fill my days taking care of my pets. This January, I took up a project of re-populating the squirrel population. I have a scope and watch them from a distance, and it's going well!
Recently I've been getting into mini documentaries on YouTube-- whether it's about cool urban legends, or serial killers, criminal psychology, etc. Other times, I'm playing videogames (Nier: Automata or Rainbow six siege-- both top-tier) or playing some guitar so i don't get rusty lol