This blood-soaked debut of Quentin Tarantino has a variety of random things to spot, but one of the most interesting is this. After Mr. Orange passes out, Mr. Pink and Mr. White go into the next room to talk. Take a look at the counter in the background - matching the character names, there are some white and pink containers together on one side, with some orange containers by themselves at the other end.
Willy Wonka & the Chocolate Factory
Slightly cruel, but you've got to chuckle. In the beginning of the movie, when the candy store owner is singing the candy man song, there's a spot towards the end of the song where he lifts up his counter to let all the kids in. Watch the little blonde girl on the right - she gets smashed right in the chin by the counter.
Ace Ventura: Pet Detective
We find out at the end of this movie that the character played by Sean Young's actually a man (if that's ruined the film for you, it's 14 years old, so you've had enough chances to see it). There's actually a subtle...ish (and enjoyably crude) clue to her real gender - when Ace goes into "her" office to tell her that he's solved the crime, in the shot from behind her, on the right of the desk, you can see a banana placed between 2 apples, which reminds me of...something.
Terminator 2: Judgment Day
More a random coincidence than a hidden reference, but has a degree of spookiness. The movie being about the start of a major worldwide war (with a heavy use of technology too), this is seen in the first truck chase sequence. Just as John and the Terminator speed under the bridge that the T-1000 crashes into, a message on the bridge can be read which says "CAUTION 9-11". The truck smashes right into it.
Arguably Brad Pitt's finest work to date, and an awesome movie. Pay attention when Ed Norton's putting Helena Bonham Carter on the bus - in the background's a big sign for a theater showing "Seven Year in Tibe" (ie. Seven Years in Tibet), another Brad Pitt movie.
Shaun of the Dead
Gotta love some comedic horror, and they don't come much better than this. Watch carefully near the end of the movie as the heroes emerge from the cellar - to the right of the screen you can see Chris Martin, lead singer of Coldplay in a zombie cameo. Worth looking for if you're a Coldplay fan, or in fact even if not - just pretend the walking dead got him.