Can a character benefit from multiple nightsticks (Libris Mortis 78) or multiple orange prism ioun stones (DMG 260)?
Neither of these items provides extra bonuses in multiples. The rules for stacking (Rules Compendium 21) do not allow untyped bonuses to stack if they come from the same source. However, this does lead to an interesting question: Could a character use a nightstick and then grab a second nightstick to use? The Sage recommends Dungeon Masters limit the nightstick and similar items to one a day.