WordPress – Poedit: Translation Secrets
The complete functions list that it needs to know about are these (as of WordPress v.3.4.2):
__()
_e()
__ngettext()
_n()
__ngettext_noop()
_n_noop()
_x()
_nx()
_nx_noop()
_ex()
esc_attr__()
esc_attr_e()
esc_attr_x()
esc_html__()
esc_html_e()
esc_html_x()
_c()
_nc()