In real life, the number seven means alot of different things. Seven goes back as far as some old religions of the middle east region.
--seven days in the week
--seven colors in a prismatic rainbow
--seven different notes in an octave
--seven wonders of the ancient world
--the seven deadly sins
--the seven circles of hell
--Akira Kurosawa's The Seven Samurai
--Disney's Snow White and the Seven Dwarves
--in American football, a touch-down and a field goal will give your team seven points
--of course, Final Fantasy VII
In addition to all these (and more) relations to seven, FF7 has it's own devotion to the number seven.
--Seven main characters: Cloud, Barrett, Tifa, Aeris, Red XIII, Cait Sith, and Cid.
--Seven head Shinra employees: Pres. Shinra, Rufus, Reeve, Heidegger, Scarlet, Hojo, and Palmer.
--The Shinra building has 70 floors.
--Lucky 7's: when your HP is at 7777.
--Sector 7 and Tifa's 7th Heaven.
--7 years between Cloud and Tifa's promise and the flashback of the same.
--Seven characters (Cloud, Barrett, Tifa, Aeris, Red XIII, Yuffie, and Cid) have seven different limit breaks.
--(SPOILER)After you defeat Hojo on the Sister Ray, there are seven days until Meteor hits.
--The Buster Sword's blade has seven corners.
--(SPOILER)Sephiroth slashes or stabs seven known characters with the Masamune (Pres. Shinra, Tifa's father, Tifa, Aeris, Tseng, Cloud, and Zack).
--(SPOILER)In the final battle, Sefer Sephiroth has seven wings.
--After Cloud's first battle, his level goes from six to seven.
--(SPOILER)Tank #7 was faulty on the Shinra 26.
--(SPOILER)There are a total of seven targets in the battle with Hojo.
OK, I just wanted too post this as a "hey, that's pretty cool" thing. But feel free to add some more significant sevens to this.
EDIT: Oops, forgot there were spoilers in here.