Serious Sam: The Random Encounter (2011)

Serious Sam: The Random Encounter plays a mixture of an action role-playing game and a Japanese role-playing game. During the open world sequences, the player may roam around freely, but can eventually hit on a randomized mob wave of enemies. These mob waves consist of ridiculously high numbers of enemies of all kinds, where the player is given the task to gun these down. (wikipedia.org)
Game Information
Genres: Action, Role-Playing
Platform: Windows
Franchise: Serious Sam
Developer: Vlambeer
Publisher: Devolver Digital