A version of Photoshop "Fade" operation (found in PS "Edit" menu), but operating of the last 3dsmax edit operation (transform, parameter, etc).
The most common thing I hear with client reviews is "How about 70% less?", a simple slider that lets you dial down (and/or up) the last operation would be fantastic.
Internally we started creating a maxscript helper for this (by just listening and recording the last operation), but it got bloated very quickly and ended up being too slow / cumbersome for real usage.
In an ideal world it would be incorporated into a tool that has the history of past operations as a series of sliders.
Important is also the functionality to go beyond the original 100% (which doesn't make any sense for Photoshop but in 3dsmax it makes a lot of sense).
