We classified into 17 major classes all the some 10^6 galaxy
spectra in the final SDSS/DR7 (ASK classification; Sanchez Almeida et al.
2010, ApJ, 714, 487). The procedure allows us to determine the goodness
of the classification for each individual spectra and, therefore,
to identify those targets which do not fit in the classification.
We expect a significant part of these outliers to be failures of the
automatic SDSS reduction pipelines. However, a fraction represents
genuine unusual objects which deserve detailed follow up work to assess
their nature. These targets provide a unique opportunity for GTC to carry
out serendipitous discoveries. In this poster we will present some
of the most promising targets.