  We show that the fluctuations associated with ferro orbital order in the
$d_{xz}$ and $d_{yz}$ orbitals can develop a sharp resonance mode in the
superconducting state with a nodeless gap on the Fermi surface. This orbital
resonance mode appears below the particle-hole continuum and is analogous to
the magnetic resonance mode found in various unconventional superconductors. If
the pairing symmetry is $s_{\pm}$, a dynamical coupling between the orbital
ordering and the d-wave subdominant pairing channels is present by symmetry.
Therefore the nature of the resonance mode depends on the relative strengths of
the fluctuations in these two channels, which could vary significantly for
different families of the iron based superconductors. The application of our
theory to a recent observation of a new $\delta$-function-like peak in the
B$_{1g}$ Raman spectrum of Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ is discussed.
