Gary's link to teh Dev site is a classic "Bug Tracking" scenario. The great thing about Trackers is that they have evolved into a full form building application.
Here is a link to some forms that use "Pretty Trackers" In other words Tiki also allows you to easily style for forms as well. There is also options to add in "Workflow" or "Logic" to your forms.
There are many other examples but these are some of the newer ones and I know that others have done some incredible work with Trackers but they are on private sites. Difficult to demo.
I hope this gives you a good glimpse as to what Tiki Trackers can accomplish.