We present recent DO results based on approximately 1 fb$^{-1}$ of $p bar{p}$ collisions at $sqrt{s} = 1.96$ TeV recorded at the Fermilab Tevatron. Preliminary results on a search for the flavor changing neutral current process $D^+to pi^+mu^+mu^-$, a measurement of the CP violation parameter in $B$ mixing, $epsilon_B$, and a two sided limit on the $B_s$ oscillation frequency $Delta m_s$ are presented. The limits on $epsilon_B$ and ${cal B}(D^+to pi^+mu^+mu^-)$ are the worlds best limits. The two sided bound on $Delta m_s$ is the first direct indication by a single experiment that $Delta m_s$ is bounded from above.