Holy Relic
A model bearing a holy relic may reveal it once per battle. This may be done at any time, as long as the model with the relic does not move on the turn it is shown.
On the turn the relic is revealed, all friendly models that are within 2D6" get a +1 Attack bonus for the rest of that turn. The relic may be revealed in an opposing player's turn if you wish.
Errata — Chapter Approved: Codex: Imperial Guard Q&A (v1.0): A Priest's Righteous Fury makes him "always count as moving even if stationary," which could seem to conflict with the Holy Relic's "does not move on the turn it is shown" restriction. For this purpose, 'move' means actually moving the model (or the unit it's with) during the Movement phase — Righteous Fury's always-counts-as-moving effect (which is really about disallowing heavy weapon fire) doesn't itself prevent revealing the Relic.