Ranked in these QuestionsQuestion Ranking
Pro Extendable with Plugins
If the default sounds aren't enough, you can extend Lightning bug with both free and paid plugins. Go here for the full list.
Pro The default free version is great
Lightning Bug doesn't bug you to upgrade or without important features if you don't pay.
Pro Almost 200 sound samples and loops
Pro Lets you mix mutiple sounds together
Pro Is also a great alarm clock
While it's in use you can see a clock as well as set alarms.