In Descent, can heroes jump over arbitrary tiles or just pits?
I don't know about the general case, but the official FAQ does specify that you can NOT jump over water tiles. They give a pretty lame justification for it, but the real reason is that it would break a lot of the scenarios that count on that to act as a barrier. So a good rule of thumb is probably that you also can't jump over "trigger" type tiles that a scenario's challenge is built around. Unfortunately I can't find anything official to back that up, other than the rulebook only specifically mentioning pits in regards to jumping and the FAQ specifically saying you can't jump over water.

That said, in all our games, we always allowed jumping over damaging tiles such as lava, too. Spending the extra extra movement point to avoid a wound (which is pretty much why you'd jump over a pit, too) seemed balanced.