Scars

Wizards seem to earn their fair share of scars while tangling with Dark Wizards, Dark Creatures, or Dark objects, and can’t seem to hide them with magic.

• Albus Dumbledore told Minerva McGonagall that he had a scar shaped like a map of the London Underground on his knee, which came in handy (PS1).
• Alastor "Mad Eye" Moody had been through so many battles with Death Eaters that "every inch of skin" on his face was covered with scars," and his hands were just as bad (GF12).
• Bill Weasley has lasting scars on his face after being attacked by the werewolf Fenrir Greyback, even though he was not in wolf form at the time (HBP 29, Pm: Werewolves). In fact, Harry thought the scars made Bill resemble Mad-Eye Moody (HBP30). His wife Fleur overlooked the scars and loved him even more: "What do I care how he looks? I am good-looking enough for both of us, I theenk! All these scars show is zat my husband is brave!" (HBP29)
• The Death Eater Augustus Rookwood had a "pockmarked" face covered in scars; whether these are from illness or spell-damage is unknown (OP26)
• All Death Eaters have scars in the form of the Dark Mark on their arms that when touched will summon the others in a form of Protean Charm (GF33, GF36).
• In fifth year, Ravenclaw Marietta Edgecombe fell victim to a "snitch jinx" put on the Dumbledore's Army sign-up list by Hermione Granger. When Marietta betrayed the group by telling Umbridge where they met, the word "sneak" appeared written across her face in pimples (OP16). The effect was long-lasting, and Marietta still had her face covered as they started sixth year (HBP7).
• The Dragon chained in the Gringotts Vaults was scarred across the face from hot swords the Goblins used to control the beast. The dragon was conditioned to retreat from the vaults when it heard metallic sounds made with "clankers" because it feared the pain (DH26).
• Neville Longbottom had "deep gashes" on his face from being tortured by The Carrows -- Ron commented "they’ve used you as a knife sharpener" (DH29).
• Ron Weasley had deep scars on his arms from being attacked by brains with tentacles at the Department of Mysteries. Madam Pomfrey applied Dr. Ubbly's Oblivious Unction which did a little good, but she also observed that "thoughts could leave deeper scarring than almost anything else" (OP38).
• When Arthur Weasley and his future wife Molly were caught out of their Hogwarts dormitories at four in the morning, the then-caretaker Apollyon Pringle punished Arthur so fiercely that "he still has the marks" (GF31). Arthur may possibly bear scars from being bitten by the Horcrux snake Nagini at the Departmenr of Mysteries (OP21, OP23).
• Harry Potter of course sported several scars: his famous lightning-shaped scar held a "soul-bit" that escaped from Voldemort when Harry's blood protection from his mother rebounded the killing curse (PS1), and during several detentions in fifth year, Umbridge's black quill burned the words "I must not tell lies" into his hand (OP13). After seeing Moody, Harry wondered if all Aurors were so scarred (GF25). Interestingly, after Harry grew up and became an Auror he was seen at the Quidditch World cup "sporting a nasty cut over his right cheekbone" according to Rita Skeeter (Pm). When Harry battled Nagini in Godric's Hollow, he received a scar to his forearm where the snake's fangs hit him, and at the same time the Locket Horcrux of Salazar Slytherin burned an oval shape over his heart as he watched a vision/memory of Voldemort killing his parents (DH16, DH117).

When J.K. Rowling was asked how Dumbledore got his scar of the London Underground (subway system), she answered:

"You may find out one day. I am very fond of that scar." (Edinburgh Book Festival)

As late a 2005 in the The Leaky Cauldron/ Mugglenet Interview , the author said the last word of the last book was supposed to be "scar."

Question: Is the last word of book seven still scar?

JKR: At the moment. I wonder if it will remain that way.

By the time Deathly Hallows was released, the author had changed her mind and rewritten the ending, as explained in this Interview with Meredith Vieira on NBC Dateline:

Meredith Vieira: The end of the book: I had read that the last word was supposed to be "scar."  But the last--
J.K. Rowling: And it was for a long, long time.  For a long time the last line was something like:  "Only those who he loved could see the lightning scar."  And that was in reference to the fact that as they were on the platform, people were milling around.  And that Harry was kind of flanked by, you know, his loved ones.  So they were the only ones who were really near enough to see it, even though peo-- other people were looking. And it also had a kind of ambiguity.  So it was-- is the scar still really there?  But I changed it because I wanted a more-- when I came to write it, I wanted a very concrete statement that Harry won.  And that the scar, although it's still there, it's now just a scar.  And I wanted to say it's over.  It's done.  And maybe a tiny bit of that was to say to people, "No, Voldemort's not rising again.  We're not going to have Part Two.  Harry's job is done."  So that's why I changed it.
Meredith Vieira: To "all is well." And you knew when you came up with that line, that was it.
J.K. Rowling: It just felt ... I felt a kind of (SIGH).  And that's-- that felt right.  And I really wanted Harry to have some (peace). (Today2)