INVESTMENT AGREEMENT effective as of December 17, 2007 among THE O’GARA GROUP, INC., WALNUT INVESTMENT PARTNERS, L.P., WALNUT HOLDINGS O’GARA LLC, HAUSER 43, LLC, MARK J. HAUSER, MARGIE HAUSER, PMR, LLC, BULLIMORE LIMITED, WILFRED T. O’GARA, KURT M....