A plumber's putty is the most common sealant for leaking pipes. However, we can't rule out other sealants such as silicone and Teflon tape. There are various sealants out there that come in handy in different circumstances. For instance, Teflon tape works best for threaded pipes, and silicone is applied on the exposed areas; whereas, putty is best for internal use. The best sealant would be the one that suits best for your situation.