Just going through some old notepads from previous employment and found a table that I'd come up with to 'rate' all the developers in the department (I was a team lead there at the time - I also rated myself and the other team leads). The purpose was to effectively work out who to put where - i.e. what teams. It's pretty a simple process, and is essentially a straw poll on some high-level KPI's, but assumes you're experienced, and 'pretty good' yourself, and can recognise/score people objectively and consistently. If you let personal preference get in there then your results mean nothing.
Each person is scored on 4 categories as some may be stronger in different areas. Each score is on a scale of 1-10, and the scores are simply added to get the overall rating ( out of 40). You can obviously make this a percentage etc if you wish. You could also apply an average to scores given by multiple people.
Team leads can obviously be rated as developers too...