Have You Played? is an endless stream of game recommendations. One a day, every day of the year, perhaps for all time.
Sub Commander is a delight: a freeware roguelike set aboard a submarine in which your band of Russian officers are as likely to perish from malfunctioning underwater equipment as from enemy fire.
Each life begins with your underwater coffin bobbing by a nearby port. Ordering one of your men to check the radio will bring fresh orders, in the form of global coordinates to visit and a bogey to kill. You descend, make your way across the world map, and hope you don't run into trouble before you find and destroy your target.
Trouble can come in many forms, be it enemy subs, enemy ships, or simply something important breaking while you're submersed. You'll quickly learn a set of standard operating procedures, ordering your officers to arm themselves with breathing apparatus or repair equipment so you can respond quickly to fires, radiation leaks or hull breaches. Still, disasters will mount one on top of another, such as a fire in the missile storage area causing explosions which breach your hull, and flood waters to fill your cabins, separate your men from repair equipment, and hamper your ability to surface.
I adore roguelikes, but I now tire quickly of stories of lone adventurers and fantasy settings. Sub Commander gives me something different, with all the drama and peril of permadeath, all the accuracy of a serious simulation game, and with controls and an interface that is surprisingly intuitive at times. At times. It's already great fun as of version 0.25, is completely free, and plans to always be completely free. You can download it from this forum thread.