These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The score generally. Bernard Herrmann's last and best work.
Fridge Brilliance: Easy Andy tells Travis a great deal about the guns he's buying, but it's all very inaccurate and leaves one wondering why an arms dealer wouldn't know his own merchandise. Then one realizes Travis probably doesn't know anything about the history of the merchandise he's buying and Andy is just telling him this stuff to convince him to buy it.
Harsher in Hindsight: Knowing about the real-life Bernie Goetz case (which happened eight years after the movie came out) can make watching Travis' shooting rampage much more uncomfortable.
Hilarious in Hindsight: Wizard's line about California being more progressive than New York when it comes to gay marriage is rather funny since, of the two states, New York has legalized gay marriage first.
Jerkass Woobie: Travis is extremely violent, racist, homophobic, and an overall sociopath. But he's so full of despair and beaten up by his problems its difficult not to feel for him. This is a guy whose life is so sad he has to send his parents letters documenting elaborate fantasies about working for the Government and having a girlfriend.
Misaimed Fandom: The film has badly suffered from being idolized by gun-toting sociopaths who believed they'd found their representative in Travis (Most infamously John Hinckley Jr). The other side of the fandom is nutjobs who take Travis' racism and vigilante ways as something to be admired. Like A Clockwork Orange five years earlier, a brilliant work of art that suffered because it was viewed by dangerous idiots.
Nightmare Fuel: The final shootout is very bloody and definitely not something to cheer on. Special mention goes to the man who gets almost his entire hand blown apart by the 44 magnum.
One-Scene Wonder: Martin Scorsese's cameo as a psychotic passenger that Travis picks up. Apparently Scorsese never planned to be in the scene, the actor they hired got sick on the day of the shoot and so Scorsese had to step in.
Never Live It Down: John Hinckley trying to emulate Travis by shooting Ronald Reagan. Not that any sane person would ever see that link otherwise, though.
A never released, video game was in the works. According to to oneof the staff, it was going to be a GTA Clone, written by Hollywood Writers who had never played a video game or seen the movie (beyond the mirror scene) before. Featured stupid dialog with awful voice acting and made Travis a mass-murdering psychopath instead of a deranged loner posing in the mirror. It even went through a period where the license was removed from the game before getting it applied again.
Paul Schrader has noted that he and Scorsese have regularly halted, blocked and stalled attempts to license Taxi Driver spin-offs.
"We really have fought over the years to keep people's hands off Taxi Driver, to keep it from being a video game and to keep it from having a sequel. It's a one-off kind of film."
The Woobie: How could anyone not feel sorry for Iris, considering the situation she was in?