Awarded by Cambridge ESOL syndicate. A very good course developed in England and available worldwide. Offered in Ireland by International House Dublin, Language Centre of Ireland and University College Cork.
Downsides may include 1) the exclusion of teaching children at a time of great demand in this market (there is a separate course for teaching children), 2) high cost incurred by examiners’ expenses in travelling often from England, and syllabus coordination worldwide, 3) inflexibility of course content and pass rates due to adherence to a strict syllabus
There are many more courses on offer, including those that tend to be called ‘weekend courses’. Be sure of your requirements; most importantly, be aware that although short courses may seem attractive they cannot convey the full extent of TEFL, especially if they lack substantial teaching practice with foreign learners. You should also keep in mind that if a course is not recognised by ACELS the certificate will not entitle you to teach in a recognised English language school in Ireland.