Common sense should win. However, claiming that you're making a ruling because "its common sense" when it is not, in fact, common sense, is still bad.
I tend to find that just asking the player to explain how what he did worked is a great way to avoid abuse without squelching anyone.
For example, were I to be running a game with a PC who wanted to trip a giant snake that's already laying on its belly, I might ask the player to describe how it worked. And if he couldn't come up with anything, then maybe I'd rule that he couldn't do it. On the other hand, he might say, "I chop at its face and as it rears back I kick it over onto its back." I'd allow that.
For rogues moving tarrasques, I believe the rogue's power descriptions already include descriptions of the rogue using misdirection and feints to trick his opponents into moving as he chooses. So... a plausible explanation for a rogue forcibly moving a tarrasque is already canon.
As it stands, I really can't think of much that doesn't match common sense reasonably well. The only ones that boggle my mind are the rogue's close blast powers that use ranged weapons. I totally buy throwing a handful of shuriken at a bunch of guys, but I don't buy rapid firing a crossbow like its a mac10.