それぞれの意見を聞かせてください。
Please tell me each of your opinions.
They each chose a different path.
A and B are 10 and 20, respectively.
Each person's opinion should be respected.
Each student has a different dream of their own.
Each participant gave their own impressions separately.
それぞれ means 'each one respectively' without implying sequence, while 一つ一つ stresses going through items in order or examining each carefully.
それぞれ is the general, everyday word for 'each' and works for both people and things, while 銘々 is more strongly tied to individual people acting on their own.
それぞれ can describe things or people and often means 'respectively,' whereas 一人一人 is limited to people and emphasizes individual attention.
Rarely used kanji form.