And another ANGEL came out of the TEMPLE which is in HEAVEN,
This is the second angel who received his orders in the heavenly temple. The first one is noted in verse 15. Again, Jesus said angels would be used to do the actual judgment acts in the end of the age (Matthew 13:47-49-52).
That this angel comes from the TEMPLE denotes this will be a "religious" harvest, i.e. a separation of FALSEHOODS (LIES) from the TRUTH. As Henry Morris suggests, coming from the TEMPLE would make this one of the 'presence angels' (Revelation 8:2).
and he also had a SHARP SICKLE.
This can only denote a destructive (not good) purging. Those who will be cut by this SHARP SICKLE are those who exchanged the TRUTH of GOD for a LIE (Romans 1:18-25-32).
This SICKLE will be different than the one used in verse 14. This one is more curved to selectively cut the clusters of grapes (in the next verse). The SICKLE in verse 14 may be more like a scythe and makes a broad cut. Both SICKLES are equally effective because they are SHARP.