CZW
Combat Zone Wrestling is an independent wrestling promotion based in Philadelphia that is well-known for its brutal, hardcore style of wrestling.
If this sounds like ECW, that's the intention. CZW was originally a backyard promotion formed in 1999 by John Zandig in New Jersey, but soon after ECW's demise in 2001, CZW began running shows in the famous ECW Arena. By the time of the Arena's closing in 2012, CZW might have actually surpassed ECW in the amount of shows run at the Arena.
As stated before, CZW is most well known for its "ultraviolent" wrestling. Its huge events, the "Cage of Death" and "Tournament of Death", certainly support this perception. However, most CZW shows feature very few actual hardcore matches, and its "Best of the Best" tournament is meant to showcase pure athleticism and not guys hitting each other with light tubes.
Due to being based in Philadelphia, CZW has close ties to Ring of Honor and CHIKARA, frequently sharing talent with both, a long invasion-style feud with the former, and a brief merging of wrestling schools with the latter. Most popular wrestlers on the indie circuit have worked at least one match in CZW. As of this writing (April 2012) former CZW talent Claudio Castagnoli is on the main WWE roster, and former World Champions Jon Moxley and Chris Hero are currently in WWE's developmental program (the former working an angle with Mick Foley!).
CZW is also infamous for its prominence on popular Internet series Botchamania, and is one of few promotions to actively encourage it.