Genetically modified organisms are organisms, the genes of which have been directly modified. 'Genetically modified organism' is often abbreviated as 'GMO'. GMOs are most often food species.
Hypoallergenic cats were created that do not cause allergy in humans (actually it was done using selective breeding, not genetic modification).
The change is to a protein that is in cat saliva. Cat's lick themselves to keep their fur in good condition and also to disinfect minor cuts and grazes. Human allergy to cats is most often to the flakes of dried cat saliva - the cat glycoprotein causes a reaction in human skin. It's a similar reason for allergy to dust mites. Dust mite 'saliva' is also designed to digest skin. It is likely that these specially bred cats are slightly defective in the effectiveness of their grooming. Their wounds probably heal more slowly with an incomplete stimulation of the normal immunity/healing reactions.
Glowing aquarium fish were created using genetic modification and a commonly used fluorescence gene . The fish are available for sale in many countries.
A cold-water fish protein which acts as antifreeze has been inserted into the genome of tomatoes, which has made said tomatoes immune to cold temperatures.