Noctis:

He is STARTLINGLY ticklish.

It’s an accident. Noctis and his S/O would be training together, and just by chance, to reach around him, they lay their hand on his side. 

It catches him so off guard that he yelps and actually warps away, sword sinking into the side of a pillar far above his S/O, holding his side and glowering like a cat that just got his tail stepped on.

The S/O would be in stitches, and it would take a while for them to stop laughing, and even longer to convince Noctis to come down. 

By the time he does, he’s fully settled into suspicion, and only lets the S/O close after multiple promises not to do it again. (And quit laughing!)

Prompto:

He’d be in a sad mood, which isn’t unheard of for the blond behind closed doors. The S/O would be trying to cheer him up, and start dancing their fingers over his ribs as a last resort, not even knowing if it would work.

At first he’d be able to hold off his chuckles, but then it quickly escalates to full blown laughter and him grabbing at their hands to get them to stop. 

“Stop making me laugh I’m trying to be sad!” he says desperately through his laughs, which only causes him to laugh even harder at the ridiculousness of that sentence. 

They both eventually settle down, and his sad thoughts would be chased away for the moment. In fact, tickling becomes a sign of affection between the two. 

Ignis:

A small gasp leaves him in surprise. He wasn’t expecting his S/O to lean over and whisper to him during a meeting. But them being shorter means that the air from their whisper was more directed toward his neck. 

Not many people know that he’s EXTREMELY ticklish on his neck. 

And to his horror, his S/O’s eyes light up with mischief upon realizing why he’d gasped. From then on through out the day, they’d delight on sneaking up on him and either blowing on his neck, or when alone in particular, gently poking and tracing their fingers on his neck which usually gets a few startled laughs out of him.

Ignis, as it turns out, if very fun to tickle when you’re in a relationship with him. Kissing his neck and blowing raspberries on the sensitive skin there is always a laugh, especially because when he gets tickled, he gets weak and can’t really fight back.

Gladiolus:

Oddly enough, Gladio is ticklish on his back. Also on his feet and under his arms, but his back is the most surprising. 

It’d be an accident when his S/O discovers it. It’s been a long day and they seem him walking down a hall in the citadel alone, about to head home. So they rush for a hug and upon puling away, their hands tail over his back with a feather light touch.

A choked laugh leaves him, and his face twists up like he’s about to sneeze from the effort of trying not to laugh. 

With a raised eyebrow, they’d dance their fingers over his back, and lightly scrape their nails over it as well, to test their theory. 

Full bellied laughs would leave him, and he’d try to get away, but since their arms would still be hugging him, it doesn’t take much to latch on and hold him hostage. 

This basically becomes blackmail material, and people are wondering what the S/O means when they say they’ll use their secret weapon against him when he’s being difficult.