As Alexis said, many binos rattle.
I was curious, so I ran a quick rattle-check on the ones to which I have access.
Here's the result:
Leica Compact (BCA, BCR) - rattle
Leica (BA, BN, BR, HD, HD+) - no rattle
Leitz/Leica original Trinovids - rattle
Meopta (Meopro, Meostar) - rattle
Nikon (Monarch, HGL, EDG, EDG II) - no rattle
Swarovski (SLC, EL WB, EL SV) - no rattle
Zeiss Compact (Conquest, Victory) - no rattle
Zeiss Dialyt - no rattle
Zeiss TFL - rattle (from a shield that moves to cover the hinge)
Of 24 binos, 9 rattled (37.5%); all were rather quiet and subtle.