The mod is Beatrun for Gmod by datae, it has nothing to do with half-life (I just used it on the HL2 maps). Download it here https://datae.org/beatrun/demo/
Other mods used in this video:
Nemez Metropolice: https://steamcommunity.com/sharedfiles/filedetails/?id=2233995006
HL:A Gordon Playermodel: https://steamcommunity.com/sharedfiles/filedetails/?id=2037114120
MW HL2 SMG: https://steamcommunity.com/sharedfiles/filedetails/?id=2845399849
HD HEV Hands or whatever: https://steamcommunity.com/sharedfiles/filedetails/?id=2786713821
Music: https://www.youtube.com/watch?v=p8r_RKYjY6w
