If you're one of those players who enjoys transmog but hates it when an enchant doesn't seem to go with your weapon, the folks at Wowhead have datamined an interesting new wrinkle - the ability to transmog your weapon effects. It seems to be achieved via an item called an illusion, like this one for the old BC era Executioner enchant, that applies only the visual aspect of a specific enchant. In addition, rogues get a special rogue only effect, Illusion - Poison, which does exactly what you'd expect, as well as certain Warlords enchants having a poisonous variant just for rogues with a similar effect.
There's also another kind of enchant variant, the hidden variant, that has the same basic effect as the baseline enchant but which has no discernible visible effect.
This is all pretty interesting stuff if you're an enchanter, or into transmog, or just don't like a specific enchant effect and want everything to look like it's got fire or butterflies on it. Ooh, fire butterflies.