The Scholar's Mate
Best way to defend against it is to stop playing <1200 rated players. Everybody tries to pull that crap.
There are too many good replies against 2. Bc4 such as 2...Nf6, but if 2...Bc5 is played and 3. Qh5 comes next, there will be only a few good replies against the scholar's mate threat. 3...Qe7 would be my reply against it.
2.Nf3 is the best.
I'm amazed. I learnt this game 10 days ago and I can't believe humans are this slow to learn this game.