Call Recorder - ACR is a nice tool which lets you record your phone conversations with ease. The user interface rocks a very intuitive layout in which you can manage all of your recordings. Each time someone calls you, this application is able to record that conversation and store it on your device. You can configure the output location and even format.
This audio file can be saved as FLAC, MP4, MP3, 3GP, OGG, M4A, WAV and AMR. The cool thing is that you can keep your recordings private by protecting them with passowords. This way you can protect yourself against nosy people that might put their hands on your smartphone. Keep in mind that this app has an auto-delete feature and in case you have an important call recorded, don't forget to mark it as such.
If somehow Call Recorder - ACR delets a conversation and you want it back, try to use the Recycle Bin component to get it recovered. The included search feature makes your life easier when looking for specific recordings. Your search terms can contain contact name, phone number and note. Moreover, if you're willing to pay for the PRO version, this application enables the ability to synchronize your recordings with cloud storage services like Google Drive, Dropbox, OneDrive, etc.