Destroys all face-up monsters, when there are 4 or more monsters on the Field.
Unable to destroy face-down monsters.
Potentially destroy your own monsters as well.
You can also set your own monster and use this card to destroy 3 of your opponent’s face-up monsters (your own set monster is not destroyed), as the condition of this card’s activation requires 4 or more monsters on the Field regardless whether it is set or face-up.
Using Ojama Go! Skill is a very effective way to fill your opponent’s field with Ojama monsters that can also be destroyed along with their face-up monsters.
You can use Tenkabito Shien and Wildheart on your Field, to destroy your opponent’s 3 face-up monsters and still retain your own monsters, as they are unaffected by Trap cards. Cosmic Compass and Phantom Skyblaster are monsters that can special summon tokens which enables you to easily gauge the number of face-up monsters on the Field in order to use Needle Ceiling.
Because it's a good card? To be fair, early-pack rarities were often BS anyway. Some of the most powerful cards in the game were Rare or Common. (Magical Scientist, Fishborg Blaster, Kirin and Royal Oppression for example.)