You guys have already mentioned all the ones I wanted to. :'(
Skyline wasn't all that bad I have to say, but the ending was completely ridiculous and unsatisfying.
If I may suggest a non scifi movie that has Bruce Willis in it I shall mention R.E.D.
It's about a bunch of retired CIA agents being hunted upon by their former employer but taking the fight back to them.
If you like special agents and Bruce Willis it's a must see.
Just yesterday I saw a movie called The Lovely Bones.
It's about a girl that's killed by a guy in her neighbourhood.
Not a jolly topic but somehow the movie grabbed me and kept me watching till the end.
I don't think I want to watch it again though.
Let me take a quick look through my collection for some scifi stuff...
Hmmm... I see War of the Worlds which hasn't been mentioned here and ofcourse everybody knows what it's about so I need not summise it.
Minority Report - About a special police division that arrests murderers before they commit the actual murder, starring Tom Cruise.
A.I. (Artificial Intelligence) - About a boy who turns out to be a robot purchased by a family because they'd previously lost a child.
Armageddon - Bruce Willis is an oil driller that goes into space to destroy a giant meteor on a collission course with earth. (sounds ridiculous don't it?)
Deep Impact - Another meteorite (actually comet) collides with earth story.
Dune !!! - Why hasn't anyone mentioned this?! This is awesome. Connaisseurs will probably crucify me for this but I especially like the mini tv-series version of it starring William Hurt. Spicey.
Back to the future trilogy - Need I really explain?
The Fly - A scientist builds a teleportation device and accidentally gets merged with a fly.
Terminator movies - Just don't watch the 4th one cause it sucks big furry balls.
Paycheck - About an invention which allows the builder to see into the future where he watches himself get killed leading to an action based plot.
Apollo 13 - Not scifi, more like just sci.
Great movie though about the Apollo 13 space mission. Make time for this coz it's a long ass movie.
Fantastic Voyage - A team gets minituarized to embark on a trip inside someone's body. If I recall correctly based on a Jules Verne story.
The Time Machine - The name says it all. Apparently there's an older and a newer movie, I only know the newer one and find it very watchable.
The Core - The earths core get's destabalised and has to be restabilised to prevent everything from dying.
I Robot - I love this movie featuring Will Smith as a police officer investigating a murder which he believes to have been committed by a robot which is deemed to be impossible.
Short Circuit 1 & 2 - Bout a robot with character.
THX 1138 - The name should be interesting enough for you to go find out for yourself what it's about.
Star Trek 1 through 11 - Duh.
Star Wars 1 through 6 - More duh.
Planet of the Apes - I prefer the five old movies but I guess the newer remake is okay.
The 6th Day - A Schwarzenegger movie about cloning.
Predator 1 & 2 - Schwarzenegger beats the crap out of some nasty ass aliens.
New Predator movie - More of the nasty ass aliens kidnap people to use them ass prey in a hunting game on some other planet.
Johnny Mnemonic - Hmmm... Keanu Reeves... based in future... hmmm...
X-Men 1 through 4 - Bitching movies about mutated humans with special powers. Maybe not really sci but definitely fi.
Serenity - The movie that follows the Firefly series
Robocop 1 through 3 - No explanation necessary.
Starship Troopers 1 through 3 - Buggy aliens plan to destroy earth but after gruesome splattering around of bodyparts on both sides eventually get their asses handed to them on a plate.
Judge Dredd - Probably not classified as scifi by most people but I like it.
Demolition Man - Stallone demolishes things in future together with Wesley Snipes.
Independence Day - Everybody knows it.
Total Recall - Schwarzenegger kicks butt on mars.
Let me know if you want to know more.