The "potential roles" for ultrasound in critical care were asked in Question 2 from the first paper of 2008 as well as the identical Question 9 from the first paper of 2006. It is unclear which hidden niche of talent the college were expecting to unearth by asking this. Presumably, a population of intensivists exists which qualify for their specialty by being able to easily rattle off a list of obscure indications for ultrasonography in the ICU. Fortunately, the value of this revision topic has diminished, as these questions have not been repeated since 2008. The LITFL page on this topic is an excellent starting point - the links available there will feed an ultrasound enthusiast for weeks.
A nice article about the use of ultrasound in the ICU can be found in Continuing Education in Anaesthesia, Critical Care & Pain (Wilson and Mackay, 2012). Other excellent resources include two articles by Yanick and Marik from CHEST, "Bedside ultrasonography in the ICU: part 1" and "part 2".The list of uses offered below is a mutant offspring of all these sources.