Removing all values in a list which contains a bunch of random values. Is there any way to do that?

To remove all the items from a list:

while (ListCount (somelist) > 0) {
  list remove (somelist, ListItem (somelist, 0))
}

But in most cases, it will be quicker just to replace the list with an empty one:

For example:

someobject.somelistattribute = NewStringList()