When Raven Software announced that it was hiring an actual former mercenary as a consultant for this game, there were high expectations for this game - specifically on the theme of playing as a hired soldier with morally ambiguous goals and more-or-less realistic gun-play.
For better or worse, Raven Software is also known for injecting more than a little flair into its games - especially eye candy of the furiously gory sort. The result of Raven's collusion with said former mercenary was certainly not what this reviewer and perhaps many others expected.
The story of the single player portion places the player in the boots of a fictional John Mullins, whose name and likeness is derived from the aforementioned consultant. He and his partner start on a mission commissioned by certain interests who would prefer not to have official resources to handle the same matter. What began as yet another mission that the veterans have done several times before quickly became a quest of revenge after it went awry - as the plots of shooter games are wont to do.
This title loudly declares itself different from the rest in its genre with the purportedly revolutionary (at the time) GHOUL damage application engine. As sadistic as it would sound, the game does have a surprisingly robust damage and decapitation system for enemies in the single player portion of the game.
Players can dispose of or enfeeble their enemies by adequately shooting certain parts of their body. This gives the player some sort of tactical leeway in approaching the campaign's firefights, of which there are lots. For example, a player needing to reach a health kit that is located in another room but is being chased by persistent enemies can choose to release a quick burst of automatic gunfire at their legs to hobble them. (However, it would have been more expedient to fire somewhere near their heads as headshots are instantly fatal for most enemies.)
Killing an enemy in sensitive/critical regions results in an excruciating death animation, if said regions are not completely removed outright, which will cause said enemy to crumple into a bleeding lifeless mess. In fact, certain death animations, especially those involving shots to the trachea or guts of an enemy, can be surprisingly long and said enemy remains an actual solid in-game model - who can be further harmed if the need arises (if they happen to be blocking critical pathways) or if the player needs to satisfy his/her sadism.
Needless to say, this game is not for the weak of heart.
However, the GHOUL system also has another surprise: it allows the player to pursue a less-lethal option to dealing with enemies, namely roughing them up a bit and then shooting the weapons off their hands. Depending on how determined they are, they may either attempt to retrieve another weapon, run away or just cower - the third outcome renders them harmless for the rest of the level, though they remain in-game models that may block movement.
As is expected from the theme of the game, completing a mission by achieving primary objectives and certain secondary ones (some of which are hidden from the player) rewards the player with money that can be used to restock John Mullins with fresh guns and armor along with some other stuff for the next mission.
Unfortunately, this feature feels superficial and tacked on. It is necessary only because the game completely removes whatever he has equipped and looted from the previous mission, perhaps because of the theme of the game (where mercenaries may have to dispose used equipment in order to conceal their activities). However, the fact that the player can only purchase up to several weapons and secondary items, but only to gather whole armories of hardware in-mission (as Raven Software's games often let players do), makes it feel as if the game has not met its goal of a 'realistic' experience as a mercenary. The presence of a few improbable weapons adds to this assumption.
The plot has John Mullins traveling through locales with real-world trappings, although all of them unfortunately reveal the age of the graphics engine (id's Quake II engine) used for the game. Still, Raven Software did much to ensure that they are visually distinct from each other.
What is not distinct however, are the behavior of Mullins' enemies; most, if not all of them, are controlled using Quake II's proprietary AI, making them behave in pretty much the same way. They are certainly not completely stupid, but as such AI tends to be, are easily lured into a trap or ambush, or get popped from afar or behind cover without them responding much. The player would be removing quite a lot of enemies in this manner. They also happen to be animated similarly (despite their different appearance and supposed nationalities), and more can actually be spawned into the level if the player makes too much of a ruckus (i.e. firing away willy-nilly). Disposing them would have been quite a tedious chore if not for the always-entertaining GHOUL system.
The audio design of the game, as can be expected from a Raven Software, is very meaty, especially those associated with the horrible ways that a player can defeat enemies with. Every weapon sounds like they should (at least for those based on real-life versions). The voice-acting, while not stellar, is mostly quite competent.
The multiplayer portion of the game of course lacks the excruciating damage modeling that the goons in the single player campaign suffer from; no player would like to be hobbled semi-permanently with shots to the arms or legs. However, there are optional game modes that render the game more punishing to careless players, such as instant-kill headshots and a fatigue meter that limits carefree movement, especially the silly jumping exploit (called "bunny-hopping") that often permeated multiplayer matches in shooter games of its day (and one that this reviewer still saw despite having participated in sessions with such options turned on - punishing such fools when they eventually slow down was very satisfying, though).
In conclusion, while this game is a bundle of fun as can be expected from Raven Software, it is not much different from what said developer had offered, despite the involvement of a consultant whose help is intended to assist the design of the theme of the game. The GHOUL system, however, certainly prevents it from becoming run-of-the-mill.