Attend the tale of SARMA Cube - it is the grave for many noobs. In this strange cube some gentlemen got lost and were never heard from again. One day they all were sacrificed in SARMA Cube, the deadly complex with strange aims.
A single-player mod for Ep2 using Exciting New Gameplay Mechanics. In it, you do the usual man-shooting, but you also get to play coop with yourself! Or at least, with your clone.
In order to enjoy Titan: XCIX - Part ONE fully in 16:9 you will be required to also download this patch, which fixes issues with the VGUI stretching across the screen. Requires Half-Life 2: Episode Two.