Potential applications of mirror-image molecules include:
Enantiopure drugs: Some pharmaceuticals show different activity depending on enantiomeric form.
L-ribonucleic acid aptamers: Artificial oligonucleotides that are constructed from the mirror-image versions of their natural forms. L-RNA aptamers are highly resistant to degradation by nucleases and are currently being tested in clinical trials.
L-glucose, enantiomer of standard glucose: Tests showed that it tastes likes standard sugar, but is not metabolized the same way. However, it was never marketed due to excessive manufacturing costs. More recent research allows cheap production with high yields; however the authors state that it is not usable as a sweetener due to laxative effects.
I do worry that much mass not being digested would be trouble for you though.
Of course there is also the whole potential apocalypse scenario