Under what circumstances (after touching what) must one wash Netilat Yadayim?

The Shulchan Aruch OC 4:18 writes: These are the circumstances that one is obliged to wash ones hands: waking from sleep, after toilet, after shower, after nail cutting, after touching shoes or feet, after washing hair, after visiting the cemetery, after sexual intercourse, after blood-letting or donating, after cleaning clothes from lice, and after touching sweaty and covered areas of the body. Rabbi Ro'i Margalit