Top100 Unity errors

In my programming practice, I encountered many code construction errors. Most worse are hidden. All works, but bugfixing and extending functionality is a nightmare. I will write some which are funny or puzzling in my blog.

1. Created object shows "null" in debugger.

Suppose code:

public class LocationsDB : MonoBehaviour { ... }

locationsDB = new LocationsDB();

Why do you think, debugger can say us, that locationsDB is "null" ?