If you don't know the rules, here they are.
In the Red Corner: 11 mindless Necron Warrior automatons stand motionless, ready to activate. Can they make their Feel No Pain roles? (198 points)
In the Blue Corner: 10 Grey Hunters with 2 flamers, a wolf banner and 2 power swords are drunk and spoiling for a fight. I'm starting to feel sorry for those Necrons... (185 points)
Neither squad has an advantage to get the charge.
The gates open!
The Necrons spring into action whilst the drunken Wolves gather their wits. The marines are in cover, but that doesn't matter because the Necrons can't fire their Rapid Weapons and go last in combat anyway! Luckily one of the Grey Hunters was sober enough to remember to activate the Wolf Banner - now all the Wolf's 1s can be rerolled in this first round of the assault.
The marines recover their wits quickly and strike before their opponents. 20 attacks hit 15 times (1 reroll), causing 13 wounds (1 reroll) - ouch! 3 power weapons are permanent kills and another 3 fail their save... for now. The remaining 5 Necrons cause only one wound which is promptly saved.
The Necrons fail their morale check at -6, but somehow manage to outrun the Grey Hunters. According to the rules of Squad Showdown, this means that the battle continues. Only one dead Necron makes its "We'll Be Back" roll and returns to the fight.
Round 2 is a statistical recovery. The Wolves only cause 5 wounds, one a power weapon. A single failed save results in 1 very dead and 1 semi-dead Necron. In return they flail about with 4 attacks total, only causing another saved wound. This time though they stick around, just making their Leadership test on an 8, and the semi-dead Necron gets back on up.
Round 3 is a big suprise. The Grey Hunters miss badly, not even hitting with any power swords. They cause 3 wounds that are all saved. The 5 Necrons finally manage to kill a single Grey Hunter. The Space Wolves flee and the Necrons roll a 5 for pursuit... but so do the Wolves. One 50/50 roll away from an upset there people!
... Oh wait I forget that they still get And They Shall Know No Fear so can't be run down. Ah well it was exciting for a moment there :)
Round 4 and the Necrons already have the moral advantage for having made it this far. They lose one of their number to a power sword wound, but make their 3 other saves. In return though they can't wound. They fail their morale check, and the Grey hunters pursue with a 6. Those brave Necrons are slaughtered to a bot.
Aftermath: The first round was brutal for the poor bots, as a combination of power weapon wounds and bad We'll be Back rolling meant they lost half of the unit before they even got to swing! They really weren't able to recover from such a huge setback, and basically were never in the running.