What are some japanese slang phrases or words?
This question is one that i'm curious about and I wanted to know if there were certain japanese slang phrases or words that japanese people might say when engaged in conversation.

Question

Answer

っていうか tteiuka
つーか tsu-ka
てか teka
something like that.
those mean...we say those terms when we start responding to the other speaker in our conversation. 
Or, we often use them before showing the different opinions.
They sound really casual, and you can say them to your friends or family only.

Answer

マジで？　（Really?）
マジで！　（True)
マジやばいんですけど！　（I cannot believe It is an amazing! )

Answer

「やばい」　→　dangerous
「うざい」　→　overage friendly?
「けばい」　→　overage makeup
variations
「ヤバイ」→「ヤッベー」
「うざい」→「うっぜー」
「けばい」→「けっべー」