Actually, you are right. Terra Blade is pretty iconic.To any of the devs: Something has me wondering: In Dungeon Defenders II the Dryad is seen wielding the Meowmere. But why the Meowmere of all weapons?
It's based off an internet meme, while a weapon like the Terrablade is much more iconic to Terraria. It has also been in the game for ages while the Meowmere just came lookin'.
@Leinfors: Is this something you'd know?
And that's why Terra Blade is also in Dungeon Defenders 2, along with a number of other iconic weapons from the game.
Almost all DD2 characters use their own weapons, but the Dryad is one of only two who share weapons. In this case, she shares swords with the Squire. Thus, there are two Terraria import swords in DD2 (and 1 imported weapon for every other character as well). I know that the DD2 devs were very big fans of the Meowmere, and may have thought that it would be more exciting (and definitely more recognizable) to Terraria fans than the Terra Blade. But in my own head cannon, the Meowmere is the Squire's weapon (he's rather silly in some ways) and the Terra Blade is the Dryad's weapon. They are just interchangeable.