Guilty pleasure can refer to anything that someone enjoys, but feels guilty indulging in, or feels like they are judged by their peers for enjoying it.
Happy Birthday To You is a song sung in America and other English-speaking countries on the occasion of a loved-one's birthday. It is generally sung off-key.
Pitta is an Ayurvedic dosha or body/mind/health type that is characterized as hot and dry. It is dominated by the element of fire and is related to digestion.
An oxymoron is a self contradictory statement, where the second portion of the statement negates the first. Common examples include a tall short person.
In photography a walk around lens is a decent lens for a variety of subjects and situations. Typically it is a zoom lens with an adjustable focal length.