Challenge

Challenges are special feats that can be completed for bonus experience points (Borderlands) or Badass Ranks (Borderlands 2). The majority of them are based around points earned for kills, depending on the weapon used, damage dealt, or the species of the target. Other challenges involve vehicles, or money and loot items.

Challenge progress can be found in the quest menu by clicking the challenge icon near the top for the PC or by pressing Y-button once on the Xbox when on the mission log screen.

General challenges
Some challenges can be completed anywhere. These have 5 levels, giving 1, 5, 10, 50, and 100 Badass Ranks respectively. There are 112 general challenges.

Location-based challenges
Some challenges are tied to specific locations. These challenges have only a single level and award varying amounts of Badass Rank. There are at least 64 location-based challenges.

Trivia

 * The challenge "I am become Death..." references those same words spoken by J. Robert Oppenheimer, the "father of the atomic bomb", when interviewed about his feelings on the weapon he had designed.
 * The challenge "Who made that man a gunner?" is a reference to Mel Brooks' spoof of Star Wars, SpaceBalls.
 * The challenge "Hot! Too Hot!" is a reference to Spaceballs when Dark Helmet tries to gulp his coffee.
 * The challenge "For the Hoard" is a play on words referencing World of Warcraft, where NPCs of the Horde faction will say "For the Horde" after accepting a quest and is a possible achievement for slaying the leaders of the Alliance faction.
 * The Enemies challenge "Little Person, Big Pain" is likely a play on the title of the television program Little People, Big World
 * The Enemies challenge "Die in the Friendly Skies" is a play on United Airlines' slogan "Fly the Friendly Skies".
 * The Enemies challenge "Another Bug Hunt" is taken from a line in the film Aliens.
 * The Enemies challenge "Skags to Riches" is a play on the cliché Rags to riches which is a phrase used to describe someone who goes from poverty to wealth or from obscurity to fame.
 * The Enemies challenge "You Dirty Rat" is a line of dialogue often attributed to gangster characters portrayed by either James Cagney or Edward G. Robinson, however neither actor ever said this line verbatim in any film.
 * The Enemies challenge "Crystals are a Girls Best Friend" is a play on the title of the song Diamonds Are a Girl's Best Friend originally from the Broadway production of Gentlemen Prefer Blondes.
 * The Enemies challenge "You're One Ugly Mother..." is a partial line from the character Dutch portrayed by Arnold Schwarzenegger in the film Predator, referring, of course, to the titular alien.
 * The Elemental challenge "Cowering Inferno" is a play on the title of the 1974 disaster film [The Towering Inferno].
 * The General Combat challenge "Afternoon Delight" is a reference to the song of the same name by The Starland Vocal Band and the Rocket Launcher challenge Skyrockets in Flight... is a lyric from that song.