一か八か[ichikabachika] sink or swim
嘘っ八[usoppachi] downright lie
嘘っ八百[usoppappyaku] full of lies
嘘八百[usohappyaku] full of lies
八釜しい[kamabisushii] noisy

口八丁[kuchihacchou] voluble
三十八度線[sanjuuhachidosen] the Thirty-eighth Parallel
四苦八苦[shikuhakku] being in dire distress
四通八達[shitsuuhattatsu] traffic network extending in all directions
四方八方[shihouhappou] in all directions

双節棍[nunchaku] nunchaku (two linked fighting sticks)
一双[issou] pair (esp. of folding screens)
一卵性双生児[ichiranseisouseiji] identical twins
双紙[soushi] written work (esp. a bound text, as opposed to a scroll)
自己双対[jikosoutsui] self dual

双刃[moroha] double-edged
双暗車[souansha] twin propellers
双殻類[soukakurui] bivalves
双眼[sougan] both eyes