IVAN, short for Iter Vehemens Ad Necem, is probably one of the meanest roguelikes out there. It uses graphical tiles instead of ASCII graphics, and also features all kinds of unique features, such as a fully functional locational damage system (losing limbs won't kill you, but it sure doesn't help), flexible character development environment, and a fluid system where you can track monsters by their blood trails. Download the ZIP package and extract to a folder of your choice. Launch the program by double-clicking on IVAN.exe.