Arcanum: Of Steamworks and Magick Obscura is one of the best games I've ever played but never finished.

I've started to play it probably six times now. The most recent time just a couple of days ago on my Macbook Pro (Bootcamp).

The latest patch (from 2003!), 1.0.7.4, makes some welcome improvements from the earlier versions. The largest change is a full screen mode (no static interface that takes up half the screen), and the missions seem a bit more balanced.

Amazing Atmosphere

The best thing about Arcanum has to be the setting. Unlike your standard fantasy fare, or the post-apocalyptic, nostalgia-future setting of the Fallout series, Arcanum aims right down the middle, mixing wizards and locomotives, halberds and repeating rifles, trolls and tesla coil hats (seriously).