Phalanx is a chess playing engine with agresive playing style. It does not have its own graphical interface, but can be used with general chess interface Xboard (Winboard) by Timm Mann. There is also a commercial version that runs as a native Fritz module and thus can be used with the Fritz graphical interface.
Toga II is a chess program, derivative of Fruit created by Thomas Gaksch. It has more chess knowledge and perhaps a better search algorithm. It is based on Fruit 2.1 and is free.