One of my few favourite games of all time.
Half-Life 2 gameplay is fantastic, it has a large array of weapons ranging from Pistols the Rocket Launcher, but the most interesting gun they use is the Gravity Gun, which pulls objects toward you and then you can fire them at enemys, although this sounds difficult to do, it's the simplest gun ever, it's point and click. The Gravity Gun is used all through the game (except the start were you don't have it) it is used for solving puzzles, as a deadly weapon, retreiving objects, and more. Without it Half-Life 2 would not be the same.
The Half-Life 2 graphic engine or 'Source' engine makes all the characters and scenery come to life. Each character has the same amount of muscles in there face as you or I have, which makes the emotions look extremely real. The new Physics engine adds the icing on the cake, objects from rocks to trucks obey laws of gravity, friction and buoyancy, without the Physics engine the Gravity Gun would not work. The excellent thing about Half-Life 2's graphics is that you don't need an amazing PC to play it, I used to play it with a Geforce 4 with my 5 year old PC, and it worked at Low/Medium settings and still looked great. Now i play it with a Geforce 6600 and it works fine, but i can't have AA & AF on.
Valve hired a group of people to do the voices of all the characters in the game, and it's sounds amazing, it's like that person is talking to you rather and just talking and facing you. They guns make good noises and when grenades explode next to you hear a high pitch hum has your hearing is attack. The sounds can be adjusted to up to 7.1 surround sound as well so the experience is even more enjoyable.
The Game itself took me around 35 Hours to complete, and i was playing it too death, for a hardcore gamer it would take around 30 hours and for a laid back player around 40-60 Hours. But I go and play back my favourite levels all over again, and now i have played it over 100 Hours.
All in all this game is a must have, if you have a capable PC, even if you don't like First person Shooters you simply must give this game a try.