Hahaha, dang.

The first part is an obvious reference to laughter. There are many moments of laughter in the game so it will be difficult to narrow it down to just one. Also Heidegger and Scarlet are very well known for their unique laughs. However, I feel it is unlikely to be them as theirs is a laughter of a very different kind. Heidegger's laugh is more like "Gya ha" and Scarlet is more like "Kya ha".
The word "dang" may have been said by a few characters so I'm struggling to narrow it down. I think the most likely candidates are Barrett and Cid. Cid may say something like "Cloud would go and do some dang stupid thing" or Barrett might say "Dang it, Cloud! You spiky-headed &*%$£!!" I think it more likely coming from the mouth of Mr. Highwind though.

Okay, give me a little bit to come up with a new riddle.

The first part of this line is a clear indication that more time is required. More time for what? A reference to more time before Meteor hits? Possibly... The assault on Mako Reactor One and the countdown before escape? Not sure... The thing it reminds me of the most though is the section when Cid and Cloud are trying to obtain the huge materia from the rocket. Cid keeps asking for more time to think of the combination while you keep guessing.
The last part is in relation to a riddle. I don't recall any character speaking in riddles particularly. Some of the waffle that Sephiroth comes out with could be considered cryptic. It could even refer to the location of The Key to the Ancients as the clue to its whereabouts is "in a place even sunlight can't reach". A clear riddle if ever I saw one.

So to sum up, the main clues are laughter, Cid, huge materia in the rocket and The Key to the Ancients. If you put all those elements together, the answer becomes clear.

Is it the Buster Sword?