My team has the good old fashioned ones with the different sized holes but since I am the only one that does wiring, I just bring my own wire strippers in. I have the Gardner Bender Wire Strippers. They are small and durable and work very well unless I touch the end of the wires after eating pizza because of the grease. A few tries then and it strips no problem. They work from 10g up to about 26-28g wire. I got them at Menards for about $20. Oh and it also has wire cutters and crimping for the standard red, blue and yellow connectors along with larger bare connectors (I think it is 4-8g bare connectors)
http://www.gardnerbender.com/en/gs-394