At the beginning when the Potentials are fighting the ubervamps, when they see the second one they move away from it. You can see in the bottom right hand corner of the screen that the ubervamp already has a Potential. In the next shot you see it jump down and grab a Potential.
Towards the end while Buffy is fighting Caleb with the scythe, he throws her into a wall and the position of the scythe changes constantly between shots.
As Spike follows Buffy away from the stairs at 24:01, you can see his reflection quite clearly in the glass panels of the front door.
When Buffy is fighting the three ubervamps at the beginning, the last one she fights falls to his knees with his back to the camera. His shirt is riding up and you can see his very human looking skin as well as gray underwear sticking out of the top of his pants.
When Buffy finds Faith and the Potentials in the sewers she throws an Ubervamp across the room. When we see the Ubervamp from behind you can also see the actor's blue boxer shorts sticking out of the Ubervamp costume.
When Caleb picks Buffy up and slams her against the pillar, the wires attached to the back are visible.
When Faith is in bed and talking with Buffy, she says, "And no one else can feel it," her lips don't sync with what she's saying.
Right at the end, when Angel saves Buffy from Caleb, the shadow of a boom mic can be seen in the top left corner of the screen as Angel helps Buffy to her feet and says, "I was never much for preachers."
When Anya gets to her feet at 11:13, you can see part of a lighting instrument at the top of the frame, and to the right of it you can see over the top of the set.
There is no reason for the First to let its minion Caleb lead Buffy directly to the Scythe. To the contrary, it said specifically it needed to keep it out of Buffy's hands at any cost. Having infiltrated Buffy's organization several times by impersonating dead persons, the antagonist must have been fully aware that neither Buffy nor her Scoobies had any idea the Scythe even existed.