Oxidation States?

Metals in low Oxidation states are usually reducing agents. Is there any example of a metal in zero Oxidation state acting as an oxidizing agent.

Of course, using the pure metal itself as an oxidising agent would be really tough. However, if you use certain tricks to stabilise the negative oxidation state, it is possible. For example, π-acceptor ligands such as $\ce{CO}$ withdraw electron density from the metal. So, $\ce{M[(CO)_n]^m-}$ complexes are stable for certain choices of $\ce{M}$, $n$, and $m$. For more details see: 18 Electron Rule For Determining the Stability of Transition Metal Complexes
Consider $\ce{[V(CO)6]}$, a 17-electron complex. It would be quite happy to accept another electron to become $[\ce{V(CO)6}]^-$. This reduction can be achieved with sodium metal. So, here vanadium(0) is acting as an oxidising agent; it is itself reduced to vanadium(−1).