Cloaking, is the practice of presenting different content or URLs to human users and search engines. Some SEO landmines can be hit accidentally, cloaking is not one of them. It is a deliberate attempt to manipulate the engines, if you’re caught doing it, you can expect a very heavy penalty. Cloaking is considered a violation of Google cloaking guidelines.
Intrusive, making your visitors jump through hoops such as intrusive pop ups or many ads above the fold can hurt user experience. In Google's own words, "...difficult-to-close Ads that follow page scrolls, or interstitial pages that require an app download, can be truly distracting and make the MC [main content] difficult to use.”
Link Schemes, intended to manipulate PageRank or a site's ranking in search results may be considered part of a link scheme and a violation of Google's Webmaster Guidelines. This includes exchanging money, goods, or services for links that pass PageRank. Excessive link exchanges exclusively for the sake of cross-linking. If you choose to ignore Google’s link scheme rules, be prepared for severe ranking penalties if caught.
Keyword Stuffing, is one of the oldest spam tactics and can still get you penalized. Inserting keywords more in an unnatural or useless way is considered “keyword stuffing.” Avoid repeating keywords over and over in your headings, copy, and all other sections of your site.
Hiding, text or links in your content to manipulate search rankings can be seen as deceptive and is a violation of Google's Webmaster Guidelines. Hiding includes matching text and background colors, placing text behind an image, using CSS to position text off-screen, setting font size to zero, and more. Here is Google's SEO Documentation on Hidden text and links.