Don't forget this one! A classic for beginners.
Lesson 2: Fools Mate

In the first diagram 1. e4 2. Bc4 is not dubious, its inaccurate at most. Also the mating pattern is called scholars mate, never fools mate (which is already reserved for a Qh5 mate after g4 & f3 or f4)
In spookys diagram 3... Nxe4 is ?! (white sustains an advantage due to Qe2 tricks, d6 is theroy). 4... Nd6 was ??, as its just a terrible terrible trap

NM-or-bust thank you for your comment.
I agree after a quick check on wikipedia about the names (in swedish there is only one name). I though still consider bc4 somwhat dubious.
About SpookyRooky's diagram have I come in contact with this theme in certain Open Ruy Lopez variations.
mvh Fredrik
This is a private lesson to one of my friends, it is not intended as a normal forum. All are though welcome to learn from it and if you find any faults allowed to post the problem so that my friend will not be fooled by my humble chess skills.
Fools mate is a very common opening trap among beginners as they have won a lot of fast victories with it against less good opponents. It is rather important to be able to dodge fools mate gaining a great game against it as it in reality is a very poor opening. The standard variation of it is:
This diagram shows how weak the mate threat is when it is met in the correct way. Opening often has similar traps in them that can end games too quickly, most of them is though easily dodged without learning any variations (this one is though important to know about).
There are a few other important opening a beginner has to watch out for. This catastrophical opening is very uncommon but can from time to time show up in unorthodox games:
The last BAD opening you have to learn by heart is one I myself not long ago was exposed to. It leads to an easy win for white if black do not see his mistake:
My game with this opening was easily won but my opponent did not resign as he did not understand the position.These three variations are probably the only three opening variations a beginner needs to learn in order to survive the few first games against better opponents.
I hope you have enjoyed the lesson.
mvh Fredrik