ZDoom

Working on it. It's very simple, really. I'm using the MissileType property rather than a new one, though. See Code Submissions forum.

Yes, this trail option would be very, very helpful!

I'm all for this

Um... okay. I know that. I created the topic where you added FastProjectiles.

I'm asking a generic way to create the trail for multiple different projectiles.

FastTrail <actor> - where the actor equals the trail actor

Already in. It's called 'FastProjectile' - but it comes without a trail.

I am wondering if a generic equivalent of the MageWandMissile with the MageWandMissileTrail could be implemented for fast missiles (I'm really after just the trail effect)

As of now if a fast missile has a speed set very high, even using A_SpawnItem and other actor spawning functions per every tic will not created a smooth trail. The spawned whatever-it-may-be's are spread too far apart. The only two exceptions I've found are using +ROCKETTRAIL, which is always the same, and replacing the MageWandMissile and MageWandMissileTrail actors with your own, limiting to only one projectile with the ability.

So maybe a Actor Property "FastTrail <actor>" where you can choose the actor that spawns for the trail: For FastProjectiles.