CsGo and tf2 are some free shooters. Could always go for battle royale games like Ring of Asylum, Pub3, or (dare i say) Fortnite aswell. GTA 5 is another fun game for shooting, driving, and fooling around.
I currently am into Doom3. A $5 fps from 2004 that could pass as 10 years newer with all of the settings cranked @4k.