This was the biggest battle I've yet played with my Adeptus Mechanicus, pulling them all together for a 1,500 pt game- once again using Codex: Space Wolves. I was playing against Deke, a GW Oxford staff member. He's got a Necron army, and for this game we were road-testing some unofficial Oxford house rules for the Necrons. The main changes were that Gauss weapons were Rending but a bit more short-ranged, Lords were WS & BS 5, and Wraiths had Power Weapons. Plus there were points increases and so on, but that gives you the basic idea!
Army List, Battle Report & Pic: http://admech.blogspot.com/2010/06/battle-report-1500-pts-vs-necrons.html