The Therapist Gamer

Mercenary Kings is on a few platforms, including the PS4.  It has an old-school feel like Contra, but modern game mechanics like upgrades.  It's overall feel is very campy and over-the-top.  You can play by yourself or with up to three other people, either split screen or online. 

 

One of the main features is weapon crafting.  You can buy a wide variety of gun parts and put them together in hundreds of configurations.  You might form a heavy, fast-shooting machine gun with a 200 bullet clip , or a light pistol that shoots bullets that explode in a pool of acid.  You find materials throughout the replayable levels and can use them to craft new items.  It's pretty fun in a zany sort of way!