Buy Northrop Grumman ( NOC), Jim Cramer said Wednesday on CNBC's "Stop Trading!" segment. Cramer said the big defense contractor keeps winning more business. By contrast, Cramer said Wednesday's huge writedowns at Merrill Lynch ( MER) show why the financial stocks have become "a nightmare to own." Cramer counseled that investors "let these stocks come down" with more write-offs before they go shopping. Cramer also "doesn't drink Juniper ( JNPR) juice" and would buy Cisco ( CSCO) instead.