I have yet to find a chess AI that plays like a human opponent at an amateur level. Most AIs seem to do something like playing a tactically perfect game but throwing in a really bad move every now and then. Has anyone undertaken (and had any success with) the project of writing a chess computer that plays like a human?
The Chess Master series is arguably capable of doing this. It creates personalities that are defined by their personal valuation of the various pieces. Starting with the standard, rough approximations that are typically used (Queen = 8 points, Rook = 5 points, Bishop = 3 points, etc...), each AI personality has these numbers adjusted, often subtly (down to small fractions, such as Queen = 8.08 points, or Rook = 4.73 points). These different weights lead to different (and often non-optimal play) where moves are not-necessarily "bad" per-se, but rather simply valued in a way that a master would not value them.