How about enabling new weapon shooting modes or uses after reaching a certain skill with a soldier?
Examples:
- having a competent/very good in accuracy would enable a head shot or even an eye shot
![Shocked :o](http://ufoai.ninex.info/forum/Smileys/default/shocked.gif)
(remember Fallout) with sniper type weapons or all single shot weapons
- good close combat skill -> a throat slice ability with a bladed weapon like kerrblade or MM knife