There are the scripts that make your site look popular, Traffic exchanges are on the outskirts of black hat Search engine spamming - multiple submission Duplicate content/pages particularly if they are there to use slightly different keywords. Redirects in order to push traffic to other pages/sites
OK to clarify, if we are referring to a 'sandbox', this is something Google will not confirm if it exists, but refers to a virtual place where new sites sit, until rank is determined and also somewhere you get kicked to if you have been doing bad things that Google finds out about. However, just to clarify, Google have never confirmed the existence of this.
Black hole SEO is a technique that origin the usual laws of Google Physics to break down. Link juice flows into a huge body, but can never escape.
The first example of a black hole site was the wikipedia. The internal links formed a network that passed link juice from one page to another allowing obscure articles with no external links to rank number 1 in the SERPs. This #1 ranking begets natural links from external links. When a webizen wants a quick reference, they consult Google and link to one of the top results. This causes more link juice to flow into the black hole and the body’s trust becomes more and more massive over time.