I want to get in to one, but can't decide. Sorta leaning on Arabic because a few other languages use the Arabic alphabet. I think Arabic might be a little easier too.

MANDARIN

Depends where you're going

mandarin

Mandarin. Then you can immediately speak to 10% of the population of the world and 100% of the population of China and Hong Kong.

MANDARIn

From what I've been told Arabic is one of the hardest languge to learn (I'm sure theres some others ones that just as hard).
I would go with Mandarin (although I personally if I had mre choices would learn Spanish or French etc).

I am agree, cause 10 % of the world population are China and Hong Kong populations. Here is teh useful info about Mandarin
The phonology of Standard Mandarin is based on the Beijing dialect of Mandarin, a large and diverse group of Chinese dialects spoken across northern and southwestern China. The vocabulary is largely drawn from this group of dialects. The grammar is standardized to the body of modern literary works written in Vernacular Chinese, which in practice follows the same tradition of the Mandarin dialects with some notable exceptions. As a result, Standard Mandarin itself is usually just called "Mandarin" in non-academic, everyday usage. However, linguists use "Mandarin" to refer to the entire language. This convention will be adopted by the rest of this article.

if u started study chinese,it maybe a bit hard for u to remember the character and different pronunciation.
But if u go deep into it, U would find chinese may be the easiest language to learn ,because it do not has strict grammar. And if u can master around 3000 chinese character u can read any chinese newspaper.

yea arabic is reli gd language and u will find something is reli interesting ,u know if u can speak arabic u can learn and speech all the languages,alot of ppl now want to learn it soo go ahead and do it XD and its the oldest language in the world, i can speak arabic very gd :P

I am From Egypt so I can speak Arabic who want a lesson and yes Arabic is not easy as you think

It depends on your environment and how often a certain language is going to get used.
I see that your avatar says you are from TX, in that case it might be better to learn Spanish.

I'll be more interested in reading old Arabic manuscripts.
Most people dont realize it was the Arabs who introduce the Greek classics to Europe.

I would say Mandarin, for business purposes.

It really depends on what you want to do . . . I say, go for the one that you're best at! If you're fluent in one, that's a better asset than just kind-of knowing what seems to be most popular.

MANDARIN

Mandarin is more useful out of virtue of the fact that more people speak it.

Yeah, Arabic is actually quite hard, pronounciation wise. You use your throat A LOT.

How about Spanish?

thats a blatant lie. Arabic isnt even close to being anywhere near the world's oldest language. Sanskrit, Hittic, Sumer, Ancient Egyptian, and many others are thousands of years older than arabic...

Yes, but how many of those are still in use today? Maybe keri meant Arabic is one of the oldest languages in the world still spoken by millions.

Personally, I would learn Arabic for linguistic purposes, as certain languages have borrowed vocabulary from it. A lot of mathematical and scientific names especially.

I can't make up my mind, whether to pick Arabic or Japanese next next semester hmmm...