The present invention relates to wobbly balls and exercise coil springs. A wobbly ball may include a non-spherical rigid, hollow ball body formed of two halves, each half comprising an upper ladle or a lower ladle which are welded together along a central seam therebetween, and defining a hollow cavity therein. A spherical inner ball is captured within the hollow cavity of the hollow ball body of the wobbly ball, so that upon movement of the wobbly ball, the inner ball rolls within the cavity, producing a wobbly, eccentric motion. The exercise coil spring may be formed of a single coiled wire, the coiled spring including a central portion where the coiled wire is coiled to a first diameter that is constant. Opposed flared ends are provided ends of the central portion where the coiled wire is progressively coiled from the first diameter to a second diameter, which is greater.
