Many times we design our special kind of bit field to manage bitwise operations on enums. Here a simple example:

[Flags]
public enum ConsoleModiefiers
{
  Alt         = 2,
  Control   = 4,
  Shift      = 8
}

When the number of values becomes higher, we have a little readibility problem with the value for each field. A possible alternative is to use the left-shift operator

[Flags]
public enum ConsoleModiefiers
{
  Alt         = 0x0001 << 1,
  Control   = 0x0001 << 2,
  Shift      = 0x0001 << 3
} 

In term of performance we don't pay any penalties since the IL code generated by C# compiler is exactly the same, but our code is probably more clear.