It's a tactical game, if you like those sorts of FPS Insurgency or Ghost in The Shell A.K.A. Neotokyo are the only source games you're gonna find that are your style. Also, define "best" better next time.
It's more personal opinion. But it is considered one of the best. Neotokyo is considered another good one but it's rather somewhat slow and tactical gameplay, just like Insurgency but is futuristic.