They are some of the lowest delay weapons. Offensive skills will not raise on grey cons, and slowly on green, but light blue or higher is pretty descent. There are lots of ways to do it, including random easy hitting mobs or versus merc or pet in an Arena.
Some are lower damage so you can beat on a mob for a long time without killing it, and is what I prefer to do with Erandi Natasu and just zone, as he regens to full health in 2 minutes or so, versus 20ish minute respawn. Damage wasn't a concern for the list, just the lowest delay options available.