Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
HostsMan - HostsMan is a freeware hosts file manager and editor. Built-in hosts file updater
HTTP Toolkit - Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, Android, CLI tools, scripts and more.
Gas Mask - Gas Mask is simple hosts file manager for Mac OS X.
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface
SwitchHosts - Free and open source hosts management & switching app