Geckos
Geckos are small to average sized lizards belonging to the family Gekkonidae which are found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. There are an estimated 2,000 different species of geckos worldwide, with many in existence still yet to be found. The name stems from the Indonesian/Javanese word gekok, imitative of its cry. The Malay word for gecko is 'cicak'. All geckos, excluding the Eublepharinae family, have no eyelids and instead have a transparent membrane which they lick to clean. Many species will, in defense, expel a foul-smelling material and feces onto their aggressors. There are also many species that will drop their tails in defense, a process called autotomy. Many species are well known for their specialized toe pads that enable them to climb smooth and vertical surfaces, and even cross indoor ceilings with ease (it has been suggested that the Van der Waal's force may contribute to this capability). All geckos stick. These antics are well-known to people who live in warm regions of the world, where several species of geckos make their home inside human habitations. These species (for example the House Gecko) become part of the indoor menagerie and are seldom really discouraged because they feed on insects (pests).
Dangers
Wall lizards or geckos are actually quite helpful creatures as they consume the mosquitoes that live in your home ... but some people don't like them scurrying about the walls and ceilings of their home.