Visible crew/equipment: When they are at the crime scene, you can plainly see the camera and camera man reflected in Special Agent Lundy's sunglasses several times. When it is a close up shot, it is even more obvious.
Visible crew/equipment: When Claire runs away from Bob after he calls her "Ms. Bennet", you can see Bob's shadow and another person's shadow on the ground. Since no one else was standing next to them, it has to be a crew member, most likely a camera man based on the odd shape of the shadow.
End Of Days - S1-E13
Visible crew/equipment: After Lisa appears to Ianto in the holding area, she disappears, when the camera changes angles you can still see her standing in the corner of the room on the right side of the screen. (00:12:50)
Sugar Daddy - S3-E17
Visible crew/equipment: When Amanda brings the baby back to Christina, while she explains that Marc only wanted the baby to hook up with a guy, the orange T-mark is visible on the floor. (00:29:55)
Treasure of the Nation - S2-E11
Visible crew/equipment: The microphone is visible at the top of the screen when Guy confronts Marion back at Nottingham castle. (00:29:20)