I would use a portal gun and trap them in the situation where there is a portal above and below them and take their portal gun and rinse and repeat
I can't imagine a portal gun would be that hard to use, I mean if there was a portal gun controller there'd be like 2 buttons on it. And how do you plan to take their gun away in the first place? They're moving REALLY fast if you were to even trap one in a portal loop. If you were to grab onto it he'd probably just bring you through, then you'd slam into the floor. I'm fairly certain that a portal gun has quite the grip if Chell is able to hold on after doing so many gymnastic thingies. And lastly you'd only to be able to get 1 at a time. I'm fairly certain by then they figure out which button shoots the blue portal and which one shoots the orange one, the 9 could certainly trap you. Iunno man some 10 year olds are already rich from investing in stocks I don't think this'll endanger them when its 10 of them to one!
