I would like to have the ability to change a marker on an individual point of a series. One way by using the array of objects with named values on series.data by doing something like this:

data: [{
name: 'Point 1',
color: '#00FF00',
y: 0,
marker: { // different marker style for this point
fillColor: '#FFFFFF',
lineWidth: 2,
lineColor: '#FF0000'
}
}, {
name: 'Point 2',
color: '#FF00FF',
y: 5,
marker: { // another different marker style for second point
fillColor: '#000000',
lineWidth: 1,
lineColor: '#00FF00' // inherit from series
}
}, {
name: 'Point 3',
color: '#FF00FF',
y: 5
// inherited style from series
}]

And another way by using the API to get a point and get the marker and have the ability to change attributes like lineWidth, fillColor, lineColor or set a totally different marker on the point.