The addition of nuclear spins and relative abundances would be very useful for NMR. I'm sure there are a lot of other nuclear properties people may be interested in; this may require another tab.

e.g.
http://triton.iqfr.csic.es/guide/eNMR/chem/NMRnuclei.html
http://www-usr.rider.edu/~grushow/nmr/NMR_tutor/periodic_table/nmr_pt_frameset.html