Remember 3D Realms? They're still around. They're also still publishing classic '90s shooters, just in 2018. And if you happen to miss Ion Maiden earlier this year, now you have three more reasons not to.
3D Realms have announced that Ion Maiden will be getting a full console release - that's the Switch as well - by the second quarter of next year. Given that this is a modern game running on the Build Engine, this should run just nicely on the train.
Might cop some stares while gibs are flying around every other corner, though.
Ion Maiden is available now on PC through Steam's early access program. It contains a standalone prologue episode, with the full campaign launching on the game's simultaneous release. That said, you can still have plenty of fun: here's the cheat codes, including god mode and clipping. Enjoy!
Update: Small note: Voidpoint is the developer of Ion Maiden, while 3D Realms and 1C Publishing are co-publishers.