Tifa was instantly my favourite character. At the Gold Saucer I got Tifa the very first time I played the date sequence, and it was a while before I realised that Aeris was the default date :)
Here is a Tifa round-up!
WARNING: This page contains some spoilers.

Job: Bar hostess (and AVALANCHE member)
Age: 20
Weapon: Gloves
Height: 167cm
Birthday: May 3
Birthplace: Nibelheim
Bright and optimistic. Tifa always cheers up the others when they're down. But don't let her looks fool you, she can decimate almost any enemy with her fists. She isone of the main members of AVALANCHE. She and Cloud were childhood friends, and although she has strong feelings for him, she would never admit it.
Tifa + Cloud

There is always much debate on who is the main love interest of Cloud; Aeris or Tifa. Naturally, I believe it is Tifa :)
Tifa and Cloud were childhood friends and the reason Cloud joined SOLDIER in the first place was to impress Tifa. He was too ashamed to show his face when he came on a mission to Nibelheim because he wasn't a First Class soldier. Even though he didn't reveal himself he still kept his promise to Tifa and challenged Sephrioth.
Not a slut

There are two very simple reasons why Tifa wears a short shirt and a skimpy top.
One is practicality; how is she expected to swing her arms and legs around in a long skirt and a baggy T-shirt?
The second is easy to see if you remember that Tifa is not real. I am female, but I realsie a large majority of games are msotly played by males. And many many of these games feature a woman not wearing much with big boobs. For this game they picked Tifa to sell copies...although luckily many men who buy these kind of games look more at character. And look at Tifa's character; does she ever act a slut? No she doesn't, she keeps herself to herself and doesn't flaunt and flirt.
Quotes

"Words aren't the only thing that tell people what you're thinking" ~ under highwind to Cloud.

"My hero will come and rescue me...I want to experience that at least once" ~ well in Nibelheim, to Cloud when they were young.

"Tell us! Or...I'll chop em off" ~ at the Don's to Don Corneo

"Cloud I...
..." ~ Round Square ride at the Gold Saucer, to Cloud.

Got any more you think I should include? Email me with your suggestions

No one can deny what happens under the Highwind when Hojo has been defeated and Cloud orders everyone to leave the ship. Cloud remarks it's funny how nothing has really changed, referring to his feelings for her as a child. They also express much 'together-ness' in this sequence; "At least we don't have to go on alone." "It'll be alright, you said so yourself yesterday." and of course the fact Tifa fell asleep on his shoulder.
I think Tifa deserved Cloud...she never actively went for him, even with Aeris playing up to him she never counter attacked and kept her distance. And even when Aeris died she didn't exactly rush in and claim him. She waited, she remembered, and I believe in the end she was rewarded.
He even mistook himself for Zack because of his shame...and this is where the cross-over with Aeris is rooted. Aeris and Zack dated, and there were many times Aeris talked about Cloud in reference to Zack, even on the Gold Saucer date sequence she wonders if he's really himself. Aeris flirted with Cloud, but he never really played back to her...at times when she held on to his arm he remained
emotionless.