lesbo
Lesbo is not exactly a slur, but it is still used in derogatory context sometimes.
Gay terms should not be used as an insult because there is nothing wrong with being gay. Therefore, lesbo is no different. It is offensive towards lesbians, just as dyke. If a lesbian says it, it's okay as it is THEIR slur and not for others to call them even "jokingly."
(this word also means lesbian in Finnish)
people who can reclaim this term lesbians