For further detail, notice that on [mwcard=FWE05]Forcefield[/mwcard] it says the prevention occurs before the Avoid Attack Step, which is when all Defenses occur. It also never refers to itself as a Defense. Therefore, the Unavoidable trait, which allows an attack to bypass Defenses, has no effect on it. For absolute certainty though, you can also look up Forcefield on page 36 of the Rules Supplement and it tells you that it works on Unavoidable attacks there.
For [mwcard=MW1E38]Teleport Trap[/mwcard] you just have to pay attention to the fact that it never uses the word "target" when referencing the creature. That word is very important on spells and you only have to target something when it is present (or if the something is in the target bar). If the word is not present, then targeting is not required. You'll also notice that it does not mention "target" when referring to the the "zone of your choice" either (clarified on page 48 of the rules supplement), so you don't need line of sight to where you send the creature to. You could easily send the critter to the other side of a wall and really mess with him. Possibly even wall him in completely.