Shortest code to produce non-deterministic output

WinDbg, 1 byte

#

Wow! Never expected a 1 byte solution from WinDbg!

# searches for a disassembly pattern, but since there's no parameters, it looks to just return the next assembly instruction in whatever dump/process you're attached to. Not sure the logic for setting the initial address, but it does.

Sample output:

0:000> #
Search address set to 75959556 
user32!NtUserGetMessage+0xc
75959556 c21000          ret     10h

0:000> #
user32!NtUserGetMessage+0xf 
75959559 90              nop

0:000> #
user32!NtUserMessageCall 
7595955a 90              nop

0:000> #
user32!NtUserMessageCall+0x1 
7595955b 90              nop

0:000> #
user32!NtUserMessageCall+0x2 
7595955c 90              nop

0:000> #
user32!NtUserMessageCall+0x3 
7595955d 90              nop

0:000> #
user32!GetMessageW
7595955e 8bff            mov     edi,edi

0:000> #
user32!GetMessageW+0x2 
75959560 55              push    ebp

0:000> #
user32!GetMessageW+0x3 
75959561 8bec            mov     ebp,esp

0:000> #
user32!GetMessageW+0x5 
75959563 8b5510          mov     edx,dword ptr [ebp+10h]

Java 7, 33 30 27 bytes

int a(){return hashCode();}

Because Java.

MATLAB, 3 bytes

why

why provides answers to almost any question. A few examples:

why
The programmer suggested it.

why
To fool the tall good and smart system manager. 

why
You insisted on it.

why
How should I know?

This is shorter than any rand function I can think of.