If you don't own the original Half-Life already, and have ever had a passing interest in it, you owe it to yourself to pick it up now as it's only 98 cents via steam. It is/was critically acclaimed as a genre-breaking game, and with the average gaming rig of today you should be able to run it at full video settings.

Click on the image below to go to the Half-Life order site (PayPal accepted):