Homographs

Some words look identical except that the stress is on a different syllable:

• בואי, קומי, שירי, שובי - When the the accent is on the first syllable, these are feminine imperatives ("go"); when the accent is on the final syllable they are possessive nouns ("my going")
•  באה, קמה, שרה, שבה – These verbs can be either past tense (when the final syllable is stressed) or present tense (when the first syllable is stressed).

Some words are indistinguishable except for the fact that there is a mappik in one of their letters:

• אִשָּׁה (woman) vs  אִישָׁהּ (her husband) – See Bemidbar 5:29. 
• השקה (to give to drink) vs. וְהִשְׁקָהּ (to give her to drink)  – Compare Bemidbar 5:24 and 27.
• –

• The word "עֲרוּמִּים" (masculine, plural of naked) looks almost identical to "עֲרוּמִים" (masculine, plural of crafty), except that the first word has a dagesh in the "mem".
• Maidservant or Arm? –See Shemot Rabbah on Shemot 2:5, reading "אמתה" there to mean "her hand (cubit)" and Rashi pointing out that if so, it should have had a dagesh in the mem.  Without a dagesh, the word means "her maidservant".