Half-life engine is very universal. Developers can make the mod out of everything. From the funny and ridiculous mod to the action-thrilled zombie mod. Here’s one of the mod : Earth Special Forces. I dont know where do they get the names but its about Dragonball multiplayer game. Its free for download but the main half-life engine is not free and proprietary. Here’s some screenshot :
Goku is fighting Goku?
Mouse-guided Kamehame ha.