All things considered, walnut is hard to beat for a gunstock. While other woods have been, and are being used, that usually is done because walnut has been too expensive, or not available in the quantities required.
True teak is quite a bit heavier, very stable, and hell on tools. Indian rosewood is also heavy, and has a tendency to develop checks and splits. Beech is widely used, but also splits more easily than walnut, and lacks figure and color. Birch, not necessarily laminated, is also widely used, but usually lacks the color and grain shown by walnut. Maple can have good figure, but requires special treatment to bring it out, and lacks color. There are other woods in the hardness and weight range of walnut, but lacking in stability when compared to walnut.
Don't know what wood is referred to as "African teak". I would think, that if readily available, and possessing the desired properties, you would see it used by the major manufacturers.