I'm a web developer by day and a lot of the software I install on my computer (namely databases and web servers) come with an optional LaunchAgent to automate starting/stopping processes on boot. I'm wondering if there's a GUI for these types of services so I can use the LaunchAgent, then kill the services gracefully. Another great feature would be if I could turn off boot on launch and just use the LaunchAgent to start/stop a service as needed.
This seems to be exactly what you are looking for: LaunchControl
Lingon (MAS link)
It provides a nice GUI for creating daemons/agents, without writing plist file by yourself. You can also use it to delete daemons/agents that you don't want.
I found this article: https://foliovision.com/2014/01/os-x-scheduling-tools
Lingon looked very slick.
launchAgents are there to run in the background in conjunction with their respective Daemon, i.e. they have no GUI but you can load & unload them using terminal using:
launchctl unload -S Aqua /Library/launchAgents/"launchAgent's name"
"lanuchAgent's name" : enter the file name of the Agent you want to load/unload. /Library/launchAgents in OS X that is the default folder for Agents to load just replace unload with load