My most controversial one really (9/11 and diana are common as hell) is the boston bombing. I dont pretend to know what happened. But I do know that the official version contradicts itself at every turn, and what has happened after the remaining suspect was arrested has been food for thought too
Lets ignore the fact that he shot himself from inside his mouth while he was unarmed.
Wrote out a confession inside the boat...in the dark, whilst heavily injured...and with no writing instrument found(hey, maybe it went the same place as the invisible gun he shot himself with). Oh, and they never found this 'boat note' until months afterwards, despite seizing and searching the boat at the time. Whole team need to go to specsavers

And also apparently confessed to the bombing whilst heavily sedated
We have the murder of Todashev..right before he was about to 'confess' to the triple murder he did with Tamerlan
We have the prosecution/government blocking access to Dzhokhar from his lawyers, imposing SAMS on him..4 months AFTER his arrest, not immediately.. which is not necessary in this case at all.
We have/had a ridiculous amount of sealed court dockets and so on
So yeah. Something stinks.