A single finger pointing upward, which could be used to represent the number one, or to ask a question.
It is also used as something that intensifies some statement — it may serve as a symbol that the user is sure in what they say, as well as a symbol of the fact that they say something significant and true.
Index Pointing Up was approved as part of Unicode 1.1 in 1993 under the name "White Up Pointing Index" and added to Emoji 1.0 in 2015.
U+261D
U+FE0F
☝️ White up pointing index
☝️ Variation selector-16