In most Semitic alphabets, the letter resh (and its equivalents) is quite similar to the letter dalet (and its equivalents). In the Syriac alphabet, the letters became so similar that now they are only distinguished by a dot: resh has a dot above the letter, and the otherwise identical dalet has a dot below the letter. In the Arabic alphabet, rāʼ has a longer tail than dāl. In the Aramaic and Hebrew square alphabet, resh is a rounded single stroke while dalet is a right-angle of two strokes. The similarity led to the variant spellings of the name Nebuchadnezzar and Nebuchadrezzar.
Resh, along with Ayin, Aleph, Hei, and Het, is one of the letters that does not receive a dagesh by convention. In the Yemenite tradition, Resh is treated as most other consonants in that it can receive a dagesh hazak under certain circumstances. And in the most widely accepted version of the Hebrew Bible, there exist 17 cases where Resh is marked with a dagesh.
Resh is used in an Israeli phrase; after a child will say something false, one might say "B'ShinKuf, Resh" (With Shin, Kuf, Resh). These letters spell Sheqer, which is the Hebrew word for a lie. It would be akin to an English speaker saying "That's a L-I-E."
The Unicode standard for Arabic scripts also lists a variant with a full stroke (Unicode character 0x075b: ݛ), suggesting that this form is used in certain Northern and Western African languages and some dialects in Pakistan.