There are several other effects that can be used to make your song sound interesting. These are not essential tools, but can be useful. The first one is chorus.

Chorus splits the sound into multiple signals (voices) and pitches those signals slightly up and down. 

• This creates a detune effect. The detune effect itself can already sound nice as a creative choice. There is also a small movement in the pitch of the voices, making the sound move a little bit, which can also be interesting. 
• In addition, you can create stereo with chorus because the voices are all slightly different. So if you want to create a wide detuned sound, chorus is the best option.

The DAWs all have chorus plugins that will work fine. Some free examples are Blue Cat’s Chorus, Acon Audio Multiply, and Imaginando DLYM. Some paid examples are UAD Brigade Chorus, SoundToys MicroShift, and MondoMod.

Blue Cat’s Chorus

UAD Brigade Chorus 

SoundToys MicroShift