This question has been a bit challenging for me to tackle because I believe that believers have been gifted to reach a diverse group of people and what may be seen as an uncommon method, can still lead to the conversion of souls. However, here are a few methods that may be unpopular and are cautioned against by scriptures.
1. Clubbing/ wild partying: Some believers misinterpret the scriptures that tell us that Jesus was found in the company of sinners (Mark 2:15, Luke 5:32) and also the verse where Apostle Paul said he was all things to all men (1Corinthians 9:22) and so they begin to attend wild parties as a method of evangelism. Some even go as far as dressing or speaking like the unbelievers that they are trying to save, just to blend in and “fight the battle” from within.
While there are believers who have been genuinely called to minister specially to people who may have had exceptional or extreme experiences, we are cautioned in Galatians 6:1&2 to be careful as we try to pull others up. Jesus did not have to become like the tax collectors before he could reach them. We cannot rescue people from a pit by jumping in ourselves.
2. Being unequally yoked with an unbeliever: Some singles use the institution of marriage as an evangelistic programme. They convince themselves that they can be married to a “good unbeliever” and gradually win them over. 2 Corinthians 6:14 admonishes us to avoid being yoked with unbelievers. Again, this is a bit thought provoking because even as I write this, I am aware that this has “worked” for some people by the mercy of God but what I am considering even harder is the question of believers being yoked to unbelievers in a business relationship. To balance this, I will say that individuals should examine their own hearts and intents. Have you been called like the Prophet Hosea to endure a difficult relationship or is that action borne out of desperation?
3. “Morning Cry”: I am not sure there are any scriptures that speak in support or against this but personally I have always wondered about this method evangelism. I have wondered at it for quite a few reasons. Firstly, I’m not sure it is scriptural. Secondly, the security and safety of the preacher since they would have to be out in the streets almost at the break of day and thirdly, will the full message be gotten? Because many times the preacher is moving about while preaching and even passers by will not hear the full message. I just find this method of evangelism ineffective.