The throwing star - 3 points on one edge, 1 on the other - Felicity "borrows" from the police only has blood on the single-point side. All of her analysis shows the blood on the 3-point side.
When Kovar is speaking to Oliver, the stir stick in his drink disappears and reappears in his glass.
In his dungeon as Oliver is firing arrows to the back wall, we see he has 10 tennis balls already skewered into it, clearly he fires another two into the wall yet at the end when we see the wall he still only has ten tennis balls skewered into it.
John Diggle/Spartan shoots right handed but his pistol in the left handed position at his low back.