Heretic: Shadow of the Serpent Riders

Platform: PC (MS-DOS/Mac OS)
Genre: First-Person Shooter
Developer: Raven Software
Publisher: id Software
Release: 23 December 1994
Rating: n/a*
Price: $5

Doom remains one of the most well-made first-person shooters of all time, and thus, its engine was used in other games for years afterward. Heretic is one of them, and as such, its gameplay is heavily derived from Doom itself. So if you like Doom, you'll enjoy Heretic.
That's not to say that Heretic is a carbon-copy of Doom. It's in a fantasy setting (with weapons to match), and has several features that Doom does not, namely interactive environments, inventory management, the ability to look up and down (that may not seem like much today, but in '94, it was a big deal), and limited flight.
There isn't much else to say about Heretic, so I'll talk about its sequels instead:
Heretic was followed by HeXen: Beyond Heretic, which itself was followed by HeXen II. Both take the basic gameplay of Heretic and add features of their own. A class-system was added in HeXen, with the original Heretic character filed under the Mage class. Fighter and Cleric are also available. Each class was given a unique set of weapons, and different physical stats. HeXen II increases the number of classes to four, with an entirely new set (Paladin, Crusader, Assassin, and Necromancer), and layers RPG-elements on top of that. In addition, HeXen and HeXen II added multiplayer co-operative modes.
This is one of the few cases where talking about the sequels is appropriate, since not only can you buy Heretic (complete with DOS emulator so it can run on Windows) from Steam for $5, or all three games for $10. Either way, it's an excellent deal.
Play, save, and enjoy. See you next week.

--Kotaro

 *Heretic was never rated by the Electronic Sofware Ratings Bureau, as the ESRB was only three months old when the game was released, and at the time, it was impossible for them to rate every game.

Left 4 Dead 2

Platform: PC (Windows/Mac)
Genre: First-Person Shooter
Developer: Valve Corporation
Publisher: Valve Corporation
Release: 17 November 2009
Rating: Mature
Price: $20

If you ask me, Valve has not made a single bad game. So it follows that Left 4 Dead 2 is good. Actually, it's great. Valve deserves some kind of award for creating two of the best teamwork-based games out there (L4D2 and Team Fortress 2). There's not much to say about Left 4 Dead 2, since it's remarkably simple. Up to four players can play as four "survivors" (with AI controlling those unclaimed) who have to fight their way through a variety of campaigns after the zombie apocalypse. There's a pretty good variety of weapons to choose from, which is the biggest improvement over the first Left 4 Dead, which only had a handful. Only by working together with your allies will you be able to survive the innumerable hordes of zombies that will come after you.
There's also a Versus mode, where some players control the zombies instead, and try to kill off the survivors. There's actually a fun kind of satisfaction in leaping out of nowhere and clawing your hapless victim's face off.
If you like first-person shooters--and Valve's in particular--the download on Steam is priced at $20, so you should really go check it out.
Play, save, and enjoy. See you next week.

--Kotaro