Stunt player Harry O'Connor was killed when he hit a pillar of the Palacky Bridge in Prague, para-sailing during one of the actions scenes. The accident occured while filming the second take of the stunt; O'Connor's first attempt was completed without incident and can be seen in the completed film.
When the "care package" takes Xander to the basement to show his tools to him, a wedding ring is visible in some shots of the "care package's" hands, but not in others.
When XXX sneaks into Yorgi's lair to rescue Yelena, he jumps down and pushes his hand against a 'brick' wall - the wall gives noticeably indicating it is not solid.
Just in time for the theatrical release of the sequel - xXx: State of the Union - Sony Pictures released an unrated Director's Cut of the movie that runs approximately 8 minutes longer and features several new pieces of storyline and some shots of brief nudity and a much longer version of the striptease for Xander.
A detailed comparison between both versions can be found here.Be aware that the European releases of the Director's Cut might be cut due to the fact that they're based on a British master that has been altered because of the BBFC's policy regarding scenes that could have a bad influence on the youth. In this particular case a headbutt is missing. One can find a comparison between the cut European version and the uncut US version here.
Q
Who is the band playing in the opening scene?
A
The band at the beginning of the film is German heavy metal band Rammstein. They are performing the song "Feuer Frei!" off their album called "Mutter".