Tau pair production
I stumbled across this, when I wanted to compare the SIBYLL 2.3c production with the CHARMED option switched on and off. Without charm, it seems there are no tau neutrinos at sea level even with a big statistics (2500000 simulated showers in total). The reason is because the only meson, which decays into taus is D_s, which happens to be both charmed and strange, so when we switch the CHARMED off, there is nothing that could produce taus in CORSIKA (even with TAULEP and NEUTRINO options on).
Acutally, tau pair production should still occur, but as I learned from discussion with Tanguy Pierog and Felix Riehn, it is not yet implemented.