[20Nation]

English - For the whole world
Spanish - For all of south and central america
French - For half of africa and other parts of the world (I will take a big trip to africa)
Russian - For most of eastern europe and russia
Portugese or Romanian - For the women. I would say Mandarin for business, but I would never put in the time to learn Mandarin.

Even though the question is instantly fluent, I'd rather say something that could become reality. I'd say i'm about half way to finishing my 5 languages

[Greek kamaki]

For the serious monger Russian is a complete must.Czech,polish and Serbocroatian are serious assets.
To get a job in EU German or Swedish.

[Greek kamaki]

For the serious monger Russian is a complete must.Czech,polish and Serbocroatian are serious assets.

[FrenchCanadian]

English - is a given
French - my native tongue
Russian - working on learning this language right now, (and finding it quite difficult.) I have a very sincere love for Russian/Eastern European women.
Mandarin - endless business opportunities, my father lives in Hong Kong, speaks chinese french & english... basically making shit ton of money solely based on his language skills.
German - as a portal to the most prosperous European country, and most germanic languages.

Spanish - although it's spoken by a large chunk of the world population, I have very little interest in it's countries, and women, sadly. On the business side I don't find it as appealing as the others.

[Patriarch]

Spanish, Portuguese and Russian for women.
Mandarin for business.
English for white God syndrome.

[Rotisserie]

From the wiki link posted on the OP, list of languages by number of native speakers (top 10):

Quote:

Language: Native speakers (millions), % of world population

1. Mandarin: 935, 14.10%
2. Spanish: 387, 5.85%
3. English: 365, 5.52%
4. Hindi: 295, 4.46%
5. Arabic: 280, 4.23%
6. Portuguese: 204, 3.08%
7. Bengali: 202, 3.05%
8. Russian: 160, 2.42%
9. Japanese: 127, 1.92%
10. Punjabi: 96, 1.44%
    

Based on this, I would choose the top 5, except sub Hindi at #4 for another language. I have no interest in Indian women, hence Hindi and Bengali are eliminated. According to wikipedia, and personal experience, Portuguese is mutually intelligible with Spanish, so avoid the overlap. Next up on the list is a bare-knuckle showdown between Russian and Japanese.

Women vs business.
Frigid weather vs frigid personalities.
Amateur sex tapes featuring 9s vs censored tentacle porn.

Sorry brain, my dick wins out this time. The best lay of my life was eastern european but spoke Russian. Russian wins.

[Merenguero]

I'd keep the three I already have, English, Spanish, and Italian, and add Russian and Mandarin. French would of course help me in Montreal, France, and some other places, but I could get by with English and/or Spanish in most, if not all, French-speaking countries. I frankly don't know how people can survive in the United States in 2014 without speaking both Spanish and English. I personally think my life would be complete hell if I weren't fluent in both Spanish and English.

[Atavistic]

German - even though I'm very fluent, not native but a given.
English - native language obvious must
Russian - took a couple semesters of it, would great to be very fluent
Spanish - second most internationally spoken language why not.
Arabic - would love to use this in parts of Middle East like Lebanon and Dubai. Very hot women.

Any other major languages such as Chinese and French would be nice but I'd prefer the 5 ones I picked.

[scorza]

I would say

1)English (speak well)
2)Cantonese (i can speak a little)
3)French
4)German or maybe Russian or Czech or Croat (for obvious reasons)
5)Italian

[germanico]

I already have spanish and english at native level, so that leaves me with 3 choices.

3- Id say chinese for business and hot chinese chicks. Plus, I think any foreigner that speaks chinese at native level would be impressive.
4- French. Im halfway through, and would make travelling easier.
5- Either japanese, because I like the culture, or portuguese, because I like the women.

[Saladin]

English, Spanish, French, Portugese, and Russian.

I obviously know English, and I'm at beginner level in Spanish.

[kosko]

Portuguese taps you into emerging markets of Brazil and Angola. Brazilian Portuguese over the European one as it's more fluid and easier to understand. Underrated/undervalued language IMO.

[Gallego2006]

1) English
2) Spanish
3) Mandarin
4) Russian
5) French

And for the record I speak English, Japanese and Spanish.

[Biologist]

Interesting responses. Spanish and Russian seem to be universally favoured in this thread.

[TravellerJay]

Native tongue is spanish and speak english as 2nd language, very fluent, almost no accent.
So if I had to choose I d say:

1. French for Canada, France and parts of Africa, old empire colonies.
2. Russian for Eastern Europe and Baltic and FSU and Russia, of course.
3. Chinese/Mandarin for business.
4. German because is similar with English, root is same. Plus is one of the most wanted languages
5.Portuguese. Because is spoken in Portugal and Brazil and although they have their differences you can get by specially in Portugal. When people thinks about portuguese they immediately think of Brazil.

[Ruban]

English - For the whole world and the international job
French - A true wettener
Chinese - Half a billion women my style
Russian - When my country gets invaded by Russia
Spanish - WW Must have

[Handsome Creepy Eel]

Mandarin, English, French, Spanish and Russian, no questions asked

[Hispanic_Reasoning]

English and Spanish are out since I speak those two as a native. My other three:

German: To get a job in the EU and fuck around with German girls
French: fuck around in France and sometimes, girls in EU who don't know English know either French, German, or the next one on the list.
Russian: Gaming potential in FSU and parts of EE, especially for me since I LOVE white girls.

[LeightonBlackstock]

1) English
2) Thai
3) Mandarin
4) Japanese
5) Korean

'cos Asians

Would possibly swap Korean for Vietnamese/Khmer as Korea has a huge percetage of English speakers. They're in the Hagwons every night from 8 till 18

Would only learn Korean to DHV and combat xenophobia, not needed for communication in my exprience

[Switch]

English

Mandarin-already almost fluent and chinese girls love white guys. Plus the business and job opportunities that speaking chinese opens up.

Spanish-because of Mexico, Central America, South America, and Caribbean--lots of hot girls

Russian- again hot girls and a cool language

French- ultimate DHV, sounds fucking beautiful, and I have a thing for French girls

[Chewbacon]

1) english
2) mandarin
3) cantonese
4) korean
5) japanese

YELLLOWWW FEVER!

[tuffgong]

English
Arabic
Spanish
Mandarin
Russian

[GreenLion]

I already speak 3:
- English
- Portuguese
- French

Looking forward to learn Norwegian and German.

[Walderschmidt]

1) English - Native tongue, nearly whole world can speak it.

2) German - Nearly fluent already, love the language, the culture, people, and women
3) Russian - Currently learning, like the people, culture, women, very useful
4) Spanish - I currently fail at the language, yet every girl I have seriously dated managed to speak Spanish in addition to other languages
5) Japanese - Good to have one Asian language and I like the Japanese

Wald

Honorable Mentions: French/Portuguese

[Brosemite]

1) Brazilian Portuguese - (Already fluent high-intermediate near advanced)
2) Spanish - (Lower intermediate fluency)
3) Mandarin - (semi-fluent, but not literate at all...would love to attain literacy)
4) Korean - Has a cool simplistic alphabet unlike Mandarin..
5) Russian - Groundwork for all the other Slavic languages