Any instrument can be easy to play if you learn how. The easiest, however, is probably the piano or the recorder. These instruments can be used to play hundreds of songs with only a few keys. This is all depending on your skill level. If you are not musically inclined, the bongos or drums should be easier. Good luck and I hope you find an instrument that you enjoy playing!
I personally like to play Guitar. Attend Guitar classes and you will also enjoy it. I am taking my training from http://mokena.schoolofrock.com . this place is awesome because they encourage us to perform on stage via music camps.
In my opinion, it would probably be the piano and vocals and I agree with CrispyFresh that singing doesn't always sound good.
I tried taking guitar lessons and that didn't work out so well for me 'cause I didn't practice enough and it was hard for me to keep my fingers on the neck ("handle") of the guitar. And again, it just does depend on the person.
Also, I would think that drums would seem pretty easy and in my opinion, in order for to me to write a song where I wanna get my frustration out, I would be able to get it out on the drums because all people who play the drums play it differently and it would be kinda cool to pound loudly on the drums to get frustration out. It can also be played differently as well, doesn't always have to get out frustration on it.
My mom's friend's daughter told me that Piano is easier than Guitar. I asked her if it was easy, she told me it was really easy. Once again, it does depend on the person.
Actually one of the easiest intruments in the flute saxaphone and clarinet trumpet id one of the harder one actually all low brass isnt as easies as it look bc i play the flute piccolo sax and trumpet and the trumpet was the hardest to learn i have been in band sice 5th grade so yea take my advice plz