Reasoning
"You say that we've got nothing in common,
no common ground to start from,
and we're falling apart.
You'll say, 'The world has come between us.
Our lives have come between us.'
But I know you just don't care,"
-Deep Blue Something, "Breakfast at Tiffany's"
Why do I think they make such a great couple? Because in spite of the fact that they're from completely opposite sides of the war and backgrounds, as well as the problems their relationship has faced, I still believe that it could work.
First of all, they care about each other. And it's more than just Locke's "Hero Complex" as a result of Rachel's accident and death! Throughout the game each has shown concern for the other, such as when Celes specifically asked about Locke after waking up in the World of Ruin. And the loyalty confusion brought about by Kefka in the MagiTek factory hit deep for both of them, creating a temporary rift.
Furthermore, we have the Opera incident and its aftermath. Locke may have been quick to change subjects when asked about who he thought he was saving back in South Figaro, but I think that's because he had mixed emotions when asked that question. Part of him could've been still clinging to Rachel's memory, while the other, more suppressed part was trying to move on. But as we've seen, that part didn't remain suppressed for much longer; it came out when Locke tried his hand at acting after Draco and Prince Ralse were knocked out. He made a bit of an idiot out of himself, I'll admit, but inadvertently he revealed his feelings for Celes!
And everyone knows what happened when Setzer took the bait and abducted Celes. He would only help the Returners if Celes married him. This of course causes Locke to freak out, especially after Celes agrees but has "conditions," that they settle it with a coin toss. Thankfully, she rigged the toss with a certain two-headed coin from Edgar (she uses it regardless of whether or not you bring him, but if you bring both him and Sabin you get an amusing little exchange afterwards!).
We also have their combined ending from the SNES version, where Celes drops the bandana she got off the seagull and runs back to get it despite the danger. Locke panics and pulls her to safety, then chastises her for nearly getting killed over a "silly trinket." No doubt the whole scenario gave him a sense of deja vu.
On that note, for those of you doubting that the bird's bandana was really Locke's, consider this: "Forever Rachel", the in-game sad remix of his theme, plays when Celes spots it. And the point is further driven home, quite ironically, if you DON'T get him in the World of Ruin. In place of Locke, Setzer saves Celes from falling, during which we get this little exchange:
Setzer: Don't fall! Remember, you promised me you'd do your "Maria" act again! ::pulls Celes to safety:: What a woman! Your life is hanging by a bandana! ::leaves::
Celes: ::looks down at it:: This is my good luck charm... When I found this, my life took a turn for the better... Locke... Promise me someday you'll look after me again?!
The final set of evidence lies in the Anthology (Playstation) version of the game's ending, entitled "For the Lovers." The ending's focus is clearly on Locke and Celes' relationship despite the other snippets. Hell, the background music is a remix of the Aria aka Celes' Theme! Kudos to Becky for pointing this out!
"There's a lot of sick people in this town,"
-Red Guy, "Cow and Chicken"
The reason why I'm bringing this up is not because some people have paired Locke with Terra instead of Celes. That much I can tolerate, although personally I think they have more of a "Older Brother/Younger Sister"-type relationship. Rather, what I really want to address is a pairing I've seen on a few sites that utterly disgusts me: Locke and Edgar.
It digusts me not so much because I hate yaoi (MalexMale pairing), but because of how these people have twisted their relationship. Edgar and Locke are best friends at most, nothing more, nothing less. And there IS proof in the game that both of them are straight! Locke had a GIRLfriend who died in an Imperial raid, not a BOYfriend! As for Edgar, he flirts with almost every girl he sees, regardless of age! Now let me ask you, why would he be the world's biggest playboy if his sexual preference was men?