I see you met Mrs. Cobb.
- The implied horror of Cobb's alluded-to past with Mal; even explained, it is still quite creepy.
- The whole story of Mal and Cobb living for decades in a dreamscape together, to the point that they lose their sense of self in the real world and real life becomes hollow and kind of meaningless. Even before Cobb used inception on Mal to get her to "wake up", it was clear that dreaming for so long is not good for your mental state.
- The scene with the elevator that leads to Cobb's subconscious. Ariadne disobeys his orders and takes it... only to end up in the hotel suite, face to face with a pissed off projection of Mal who has every intent to kill her. Mal's Death Glare (picture) says it all.
- Mal's "real world" death. Cobb arrives at their anniversary hotel room, dressed up and with flowers. He comes in and sees the room trashed. As he comes to the balcony, he sees Mal clinging to the building across the street, ready to jump. Cobb tries to talk her down, but she mentions that she's told people she's fearful of him. He turns around, surveys the room, and realizes he's about to be framed for murdering his wife. Then she jumps.
- It is implied that the projections in Saito's dream ripped Nash apart in the opening dream sequence.
- The basement full of people in Yusuf's basement, implied to be dream addicts who come to dream for hours upon hours every day because they can't handle the real world any more.
- The ambiguous fate of Nash. While he's a cowardly worm, he is left at the mercy of a faceless, ruthless corporation apparently not above committing acts of espionage, violence and possibly even murder. Whatever fate he suffers, it most likely isn't pleasant. The last we see of him, he is being dragged away by two burly men and seems terrified.
- Dying while heavily sedated in the dream world and getting trapped there for enormous amounts of time is a rather terrifying concept. It's left ambiguous whether Saito and Cobb actually manage to wake up, potentially meaning they are trapped mentally in a world moving at a snail's pace forever while in reality they are simply comatose.
- Given how slow time moves deeper and deeper into the dream world, you could be trapped down there your whole "real" life if things went wrong. So say that's 60 years of being comatose in the real world, you would experience that as thousands or possibly even millions of years in the dream. As one character hints, that would be enough to turn anyone's mind into "mush". The main consolation is that it "depends on the dream" so better hope for a really good dream to spend time in rather than a Dark World.
- When Fischer realizes he's dreaming at the hotel bar, every single projection in the room immediately stops whatever they're doing and starts staring at him and Cobb in a robotically blank way, and all the extras are really good at making it look as unnerving as possible. From previous evidence and experiences, we know they're all this close to jumping Cobb and mauling him to death if he can't convince Fischer to trust him and trick him into believing he's a projection himself. Thankfully, he pulls it off.
- On that same note, the scene at the bridge when Ariadne is first learning to bend dreams the way she wants to. Cobb warns her not to use real world places as locations for dreams, and gets somewhat upset when Ariadne doesn't listen; as a result, the projections on the bridge all gang up on them and hold them in place while Mal suddenly steps out of the crowd with a knife in her hand, and, without missing a step, stabs Ariadne in the gut, all while the latter is screaming for Cobb to wake her up, and him begging Mal to stop. Elliot Page's performance really sells the sheer terror and panic Ariadne must be feeling as well.
