First of all, English is not my native language so I'm sorry for all the mistakes you can find below. Anyway, I hope you like this one-shot :)
I don't own anything.

He glanced at her unsure looking for a confirmation. She just bit her bottom lip and her eyes told him everything. That really was a bomb. A big one with bright red '00:00:30' on top.
Thirty seconds. That's how much time they had to disarm it or leave the place as soon as possible. Considering the fact that they were locked in some kind of warehouse, there was only one option left. They had to stop the counting or they would die.
30, 29, 28…
"I do not know how to disarm it, Tony. I have never seen something like this in my life. I am so sorry, I-"
Ziva started to panic. It was so obvious. Especially for him because no one knew her as well as he did. He heard her panting and immediately wondered when was the last time he saw her that frightened. Probably that one terrible summer four years ago.
She on the other hand felt responsible for both of them. Tony was always the funny guy but she knew he relied on her. Also this time.
"Hey, calm down."
He took her hand in his own and kissed her palm. Her heart was never beating so fast in her entire life. She wasn't sure if that was because she had less than thirty seconds left to find a way how to actually survive or because Tony wasn't making anything any easier and just kissed her palm. He. Kissed. Her. Palm.
… 27, 26, 25, 24…
"Look at me, Ziva."
She almost hesitated. Almost because they had only about twenty seconds left and she wouldn't dare to let them both die arguing. Sighing, she looked him right into his eyes showing that she was more scared than ever. At least she couldn't, or didn't want to, remember the last time the death was so close and she was so helpless. And Tony, oh Tony, he was there with her knowing they are going to die and willing to stay by her side till the end. Their shared end.
… 23, 22, 21, 20…
"This is funny" she laughed nervously. "I remember when we were stuck in the container few years ago and we thought that there is a bomb in the box. You being yourself said that I should have slept with you and now you are here acting so serious, why?"
"We're not gonna make it, Zi." he sighed lacing their fingers together. "And for the record, you should have slept with me. I surely regret not doing that when we had a chance."
… 19, 18, 17, 16…
"I am sorry I made you go here with me." she said deciding to ignore his last words.
"I'm sorry I didn't predict that as a senior field agent and I'm sorry I can't save you this time like we all did in Somalia."
She blinked back tears and placed her other hand on his cheek closing her own eyes praying that is was just a dream. She didn't want to die. Not now. Not here. Not with him. Not that she would prefer to end her life with anyone else but she didn't want that to happen now when they started relying on each other again after EJ and Ray fiascos.
… 15, 14, 13, 12…
"That is not your fault, Tony. And I am content with these four years you gave me. I really am. I am sorry that I probably did not thank you enough."
"Stop it, Zi. Seeing you being yourself again was all I needed. You coming back to work every single day, everyday more self-confident, happier, that was all that mattered."
She didn't know how to respond because she clearly didn't expect that. She didn't expect him being so honest with her. Not now. Not ever.
… 11, 10, 9…
"I wish we had more time, you know?" he continued taking a strand of her hair in his hand and placing it behind her ear. "In these ten seconds all I can do is tell you that I seriously considered spending the rest of my life with you. Besides, my dad approved you by my side many years ago. Even if only as a partner, a co-worker." he hesitated. "I hoped your relationship with CI-Ray wouldn't last long but when you almost agreed to become his wife, I lost it. That night was the first one I drank that much after Jenny died."
"Do not, please." she whispered. "I am not sure if I want to know that and die right after because I certainly have feelings for you. I just do not know what kind of feelings".
… 8, 7, 6, 5…
"You're the best what could have happened to me. I want you to know that."
"You are the best partner I have ever worked with."
"I'm glad. I really am, Ziva."
… 4, 3…
"Boss's gonna be so mad." Tony chuckled but Ziva couldn't care less. She squeezed his hand and moved closer to his body almost sitting on his laps.
… 2, 1, 0.
The exact moment when her lips touched his cheek and his lips kissed her temple, the bomb went off. But they were in this together. Till the end. The post-elevator them, the open book, baring their souls, telling each other all kinds of personal stuff. For the last time.