wtf
http://vimeo.com/49094660
This tower in downtown Caracas is nicknamed "Torre de David" after David Brillembourg, the tower's main investor who died in 1993. During the banking crisis of 1994, the government took control of the building and it has not been worked on since. The building lacks elevators, installed electricity, running water, balcony railing, windows and even walls in many places.
Venezuela's massive housing shortage led to occupation of the building by squatters in October 2007. Residents have improvised basic utility services, with water reaching all the way up to the 22nd floor. They can use motorcycles to travel up and down the first 10 floors, but must use the stairs for the remaining levels. The residents live up to the 28th floor, with many bodegas and even an unlicensed dentist also operating in the building.

By pure coincidence I was reading about this (and other abandoned skyscrapers) last month, there's a few other buildings like this around the world though this one might be the coolest one in terms of an entire functioning community popping up inside it.
This one, was completed and used for its intended purpose, and has since been torn down but basically became the tallest slum in the world:
http://en.wikipedia.org/wiki/Edif%C3%ADcio_S%C3%A3o_VitoIn 1985, the magazine Veja em São Paulo wrote that the building was "perhaps, the biggest concentration of people of the city, (with) three thousand inhabitants, mostly low-paid and informal workers and prostitutes".[4] In a 2009 article, the magazine Época stated that the building started to deteriorate in the 1980s because of the population's homogeneous poverty, differently from similar buildings such as Edifício Copan, which attracted middle-class families.[2] The deterioration was reinforced as apartments started to be split into two, and electricity started to be obtained illegally (80% of the electricity of the building was illegally supplied as of 2002[3]). Another reason was the suspension of the waste services – rubbish was then simply thrown out of the windows.,[2] with dirty water and food.[4] Inhabitants of the building could use the water from two artesian aquifers until 1982, when the Tamanduateí River flooded and polluted the water. Sabesp was so designated as the company responsible for the supplying of water, with a higher cost.[4] Only one of the three elevators was still working in 2002, but it could only reach the 15th (of the 27 floors), generating half -hour queues of inhabitants during the "rush hour".
At that time the building had already been nicknamed "Balança, mas não Cai" (It Shakes But it Doesn't Fall) and "Treme-Treme". To get access to the building, one must either be allowed in by someone who lives there or hold credibility among other inhabitants. Another option is to use police force
This one in Poland basically never had the outside built, it's the tallest building in Krakow:
http://en.wikipedia.org/wiki/SzkieletorThis one in Memphis is huge, downtown, etc. but because of some legal crap it's vacant:
http://en.wikipedia.org/wiki/Sterick_BuildingThe original lease of land for the property, dating from the late 1920s, required the $1,500 monthly payment to be paid in gold coin “of standard weight and fineness or its equivalent.” An unsuccessful 1975 lawsuit by the land owners sought to recalculate the rent at the then-current price of gold, or roughly $13,500 per month
...
The Sterick Building is a land lease property wherein the original builders leased the land the building stands on for 99 years without buying the land outright. The land and the building are currently owned separately.
And maybe the most infamous one though it's apparently "finished" now so they don't have to photoshop it out of pictures of Pyongyang anymore:
http://en.wikipedia.org/wiki/Ryugyong_Hotel
And from good ol Detroit:
http://en.wikipedia.org/wiki/Michigan_Central_Stationhttp://en.wikipedia.org/wiki/Book_Towerhttp://en.wikipedia.org/wiki/2643_Park_Avenue_(Detroit,_Michigan)