So, this one's several weeks old, but I finally figured out what I was thinking of.

I was telling someone that Banner of Eternal Flame doesn't give flaming attacks to any magical weapons, but couldn't back it up at the time. Thought I'd lost my mind, but noticed the other night that, in fact, the entry for Flaming Attacks reads:

"Unless otherwise stated, a model with this special rule has both Flaming shooting and close combat attacks (though any spells cast by the model are unaffected, as are any attacks made with magic weapons they might be wielding)."

I'm sure some (most?) are already aware of this one, but I know a few are still playing it otherwise.