I've been looking over my Tyranids codex and I've run into a few models that have various special rules for melee attacks. the Hammer of Wrath special rule states attacks are resolved at unmodified STR and AP -. However, it says nothing about special rules not applying to these attacks.
First, and most straight forward, is poison. Gargoyles and Shrikes and several monstrous critters can take Toxin Sacks giving them a 4+ poison attack. It would make sense to me that the hammer of wrath attacks now wound of a 4+ with the re-roll option for str => toughness.
If that applies then does rending? shrikes are str 4, would the attacks count as rending on a 6? Rending states that a 6 always wounds, it also states that the attack ignores armor saves. So while the attack is still resolved at STR 4 and AP -, an armor save is not allowed.
Smash, smash is a special rule for monstrous critters. Part of it states all of it's attacks in melee count as AP2. This, to me, sounds like a set modifier, as is the special rule for HoW which is a set modifier for AP. Does this follow the rules for multiple set modifiers? (essentially a coin flip).
I'm only curious about special rules, the rules for wargear seem rather straight forward in regards to HoW, your wargear doesn't apply, because your not using it. However, these are special rules that apply to all attacks made by the model.