Going Straight Back to the Source.
Reviewing Garry's Mod isn't an easy task, because one person's GMod experience is going to be drastically different from another and, more importantly, Garry's Mod is both every type of game you could imagine, and no type of game all at the same time. Let's get down to the facts: Garry's Mod was made by, well, Garry Newman not too long after Half-Life 2 had been released as a way to have fun with the Source Engine. Now, some three years later, Garry's Mod is up to its eleventh major revision and has yet to lose its charm.
But what do you do? In one word: anything. Garry's Mod is a sandbox game that gives you the "Toolgun," which, through the many-times revised and overhauled spawn menu, allows you to rig up and manipulate props- whether it be to strap Balloons to make the ultimate hovering bathtub of death, or to precisely attach wheels to a nearby mattress and then subsequently propel the thing across gm_construct (the home you will become intimately acquainted with through your first attempts to unravel this game) with thrusters that you have taken up to eleven... thousand. Already GiantBomb has a ton of screenshots illustrating the myraid of things you can create in an afternoon's session, but even those don't begin to scratch the surface. Garry's Mod is a game that you can sink literally hundreds of hours into by yourself, but the true Garry's Mod experience exists online where the Garry's Mod community comes together to unleash untolds amount of user-made content.
It is here, on the vast fields of the internet that you will come in contact with the best (and worst) Garry's Mod has to offer. What was a game about slapping (exploding) balloons to props can become a desperate hold-out with you and your new friends against hordes of zombies or perhaps creating the biggest and best defended fort of wooden boxes is more your calling. Whether you're Captain Jean-Luc Pickle of the USS Enter-if-you-dare cruising the vast expanses of sb_gooniverse, or Lohn Jocke, trying desperately to say alive on gms_stranded, Garry's Mod has something for you and you need only to find it. Of course, being a game with "NO RULES," Garry's Mod is a community where acting your age is essential but not something to expect from all users. There will come the day when the dreaded "Raging_Noob" or the more fearsome "MingeBag" appears before your creation and leaves you with "Lost Connection to Server" message.
I could continue on for many moons speaking of the wonders this package holds, but alas I don't want to keep you here too long. Going to the more technical aspects of the game, Garry's Mod has a fairly user-friendly main interface (the Spawn Menu) that will generally keep all of the various mods and accessories you're bound to come across under control if you let it (or force it). Visually, this is the Source Engine, and the only way you actually HAVE this game is if you own a Source Mod of some sort (be it Counter Strike: Source, Half-Life 2, Day of Defeat: Source, etc) and therefore, you should know what to expect. Team Garry has managed to make all of the new content itself look sleek, be it the information bubbles that pop up when you mouse over one of your things you've just spawned, or the Toolgun itself, which has its own personality altogether. Of course, manipulating the Source Engine is the name of the game, so what would this be without Post Processing? You can add untold amounts of Super Depth of Field, or blinding amounts of Bloom, so it's the same old Source visuals we've come to love but with a little more user-end chaos. But that's the norm in GMod, isn't it?
The same is all true with sound, but of course you will be coming across user made sounds that may not be the greatest things to grace your ears, or familiar tunes may pop up suddenly (Did that jeep that pass me have a Boom-Box welded to it, and more importantly was it just playing "Still Alive"?) throughout your adventures, but this is after all a Source Mod with Half-Life 2 its base, so expect to hear those sounds throughout your adventures.
Garry's Mod is a great game once you find your niche and it is a great way to blow off steam after a long day. For only 10 bucks, you're not about to go hungry buying this game (this is of course assuming you have a Source game, and I assume you do. If you don't, what are you waiting for? Go buy the Orange Box. Right now.). For everyone else who already owns this game, happy building and perhaps we may meet on the fields of freespace06_v2-1.