I was just thinking of something I want in a future map of mine, would it be possible to make a tube, like from when in SP wheatley gets sucked into the nuerotoxin tube and breaks the glass in glados's chamber, so, would it be possible to make a tube with a core falling through, but only when the player activates a trigger?

Yes, all you'd need to do is (assuming a vertical tube) place a core in the top, put a nodraw func_brush below him to stop him falling then kill the brush using a trigger. If it's a more complex tube system, I'd use a tracktrain with the core parented to it. It would start at the beginning, run through the tubes then the last path would OnPass ClearParent for the core to make it fall.