Aliens - the second movie in the series.
Once you have seen the first one and know what the Aliens can do, this movie just never stops. Everytime you think the Aliens have been defeated, they havent, and they keep coming, and you DON'T want them inside you!
The first movie was super scary too, walking thru that ship not knowing where the Alien is, they say that to heighten the effect they didnt always tell the cast exactly when the Alien would attack them or exactly where the Alien would be to get a more scared reaction.
This is one scary series, and a great blend of horror and sci-fi.
never take life seriously