If you subscribe to the idea that Gertrude was a knownig particicant in her late husbands murder, the causes of death in the last scene make perfect sence: The two gallant sons avenging a murdered fathers death is killed by the sword in honest combat while the vilainous conspirators are killed by poisoned drink, often called a cowards weapon.
Although I'd read Hamlet in High School, and knew that Gertrude's line: "Methinks the lady doth protest too much" came from the scene of her watching (essentially) an Expy of her marriage to Claudius, it wasn't until after college that I realized the significance of Hamlet's line leading up to that quote. He's basically asking her if she's enjoying the play, but the exact words he uses are: "How like you this play, Mother?". With a different inflection, this could be a statement. "How LIKE YOU this play, Mother". Brilliant.
Another piece of wordplay-related brilliance in Hamlet: Claudius' line, "My offense is rank; it stinks to heaven". It struck me at a literal fridge how layered and complex this line is, and how elegant a fusion of the tragic and the comic. Claudius' offense is 'rank' both in the sense of an unearned position (his rank as king) and in the sense that his offense is figuratively smelly and repulsive. It "stinks to heaven" both in the sense of a rising stench, and also in the sense of being repulsive to the heavens, an affront to the sacred.
It was years before I finally got the 'country matters' joke in Hamlet. Since then, I've enjoyed Shakespeare a great deal more. - Shinyfox
When Claudius prays for forgiveness in Act III, he says something to the effect of his crime being subject to the "most primal curse." But, of course, Claudius comes out of a very Christian background. What anecdote in Judeo-Christian teachings talks about a brother killing a brother?
After they finish depicting an all-too-accurate version of the murder of Hamlet's father, what happens to the Players? Claudius likely has them interrogated and imprisoned to determine the source of their information and to prevent it from spreading.
Imprisoned at best. They're out of towners, after all, and unlikely to be missed if they've already moved on from their normal place of performance.