As well as having a native alarm clock on BlackBerry 10 there are some decent third party ones too in BlackBerry World. I recently found Digital Alarm Clock which is a port but it works perfectly and I'm loving it.
The application has a beautiful green, black and white user interface and that's one of the things that first attracted me to it. But it's the functionality where things make this one stand out from the crowd.
When setting a new alarm you are given a wide range of options to choose from. At the top of the screen you set the time (which is kind of important with an alarm app). Then you need to add a title for the alarm and this will come in handy as multiple ones can be set, therefore also acting as a reminder style app. There's a decent selection of alarm tones to choose from including the Flintstones and Scooby Doo which made me smile. You can use your own music if you want but not with this free version.
You can tweak the alarm volume as well as the snooze duration and even have vibrate on or off - all easily accessible when creating an alarm.
If you fancy a change from the native alarm clock give this one a try. It's free after all.