We review magnetic and transport properties of FeSb<sub>2</sub> and Fe<sub>0.75</sub>Co<sub>0.25</sub>Sb<sub>2</sub>. Single crystals of pure and Co-substituted FeSb<sub>2</sub> have been grown using molten metallic fluxes. Synchrotron powder x-ray diffraction confirms phase purity and orthorhombic <i>Pnnm</i> space group. Cobalt substitution drives system from temperature independent diamagnet to a ferromagnet at T=0 with very small ordered moment. Application of H=70kOe enhances resistivity [ρ(H)-ρ(0)]/ρ (0) more than two orders of magnitude at T=2K. Underlying physics and possible mechanisms for the colossal response of resistivity to magnetic field will be discussed.