  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 world's 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.
