When Vincent visits his contractor, after turning down the chocolate, he is shown some "goodies he cannot refuse". When the bag is thrown on the table, a diamond rolls out onto the table. When Vincent reaches to pick the bag up to examine the South African diamonds, the loose diamond has disappeared.
When Vincent first enters his flat, he goes into his 'weapon room' and touches a crossbow to position it 'just so'. We see Vincent from behind the crossbow in close up, and the direction the crossbow is pointing is clear. However when the camera switches back, the crossbow is suddenly pointing in the opposite direction.