Tutankhamun's mummy
Detective Michael R. King and FBI profiler Gregory M. Cooper came together with an actual Egyptologist to form their own theory which was that Tutankhamun was murdered. With the use of forensic evidence and their extensive backgrounds in criminology, they came to the conclusion that he was likely murdered by one of his closest advisors, Ay. Ay did succeed Tutankhamun on the throne, so they used that as the motivation for the murder.
Smenkhkare
As shown on the box from Tutankhamun's tomb, Meritaten came to take Nefertiti's place as royal wife late in Akhenaten's reign. Marc Gabolde has proposed that Meritaten is "Dakhamunzu" and the dead king is Akhenaten, in a number of articles. He supposes that Zannanza completed the trip and died only after ascending the throne as Smenkhkare. It is after the death of Smenkhkare/Zannanza that Meritaten assumes power as Neferneferuaten.
Meritaten seems the least likely on the basis that at the time of Akhenaten's death she would only have been about 20 years old. By contrast, Ankhesenamun would have been about 25 and been queen consort for some 10 years. It seems unlikely that the young Meritaten would have the wiles to deceive Suppiluliuma, maintain her interregnum in the face of pressure to marry a 'servant' and conceal the presence of a male heir in the personage of Tutankhaten.