1) Neiros Erev Yom Kippur
2) Biur Chometz
3) Bircas Ilanos
4) The chasimah for Nachem (on tisha b’av by mincha – though some sefardim say it 3x)
Note: For those of litvish origins, the brocho of “Haposeach lonu shaarei rachamim” is also said once a year (instead of “Yotzer ohr u’voray choshech” on Yom Kippur). But some other nusachos never say it, and some others say it on Rosh Hashono as well. So litvaks could count it as a fifth.