Half Life offers a single player FPS adventure that still holds up today...
You assume the role of Gordon Freeman, a theoretical physicist in the Black Mesa Research facility in New Mexico, and you are running late for an experiment. You put on your Hazardous Environment suit (or HEV suit). When the machine turns on, you (as Gordon) are tasked with pushing a non-standard specimen into the scanning beam of the Anti-Mass Spectrometer for analysis. However, doing this knocks you out and opens a portal between this world and Xen, another dimension. When you awake, the whole research facility has been attacked by creatures from the other dimension. Now you must fight your way through these alien creatures and even the government soldiers, who are trying to cover everything up and kill all who are still alive, aliens and humans.
This game must have been fantastic in the 90's, for it does an excellent job of immersing you into the eyes and world of Gordon Freeman. You really feel like you are going through what he is. The graphics, although they might not look like much right now, were ahead of their time as well, there wasn't a game that looked this good until the Playstation 2 era. It's just kind of weird that all the scientists and security guards all look the exact same as one another with no distinction.
There are no levels throughout Half Life but a long continuous stream of locations from beginning to end, mostly in the Black Mesa Research facility, but there is still a great variety of terrains and challenges. They are, however, split up into different chapters, but there is never a jump from one level to the next and no cut scenes. You are literally in the game until you finish it, which can take up to 20 hours. The game is full of surprises though, throwing new challenges at you at every second to keep you playing.
The weapons are overall pretty good, but there isn't a large variety as, oh say, Goldeneye, but you get everything you need. You have your assault rifle, pistol, revolver, crossbow (for longer range), shotgun, etc. but you will have your crow bar as well when you run low on ammo, which you will often. The whole game is knowing when to use what weapons at what time as ammo for certain weapons might be harder to find than others. You have health and energy (like armor) which you can find scattered just about anywhere but even then you must be careful for these can also end up being scarce.
Half Life was a revolutionary game for its time for its immerse atmosphere, graphics, diverse challenges and gun play. Even after almost 12 years of release, Valve's first masterpiece still holds up today as a fun adventure that anyone can enjoy. Half Life is only $9.99 on Steam now if you wish to see for yourself.