The ability to rapidly enter new tickets, from a single page. This could work if you want to import a crude todo list (from a meeting or brainstorm session) into the issue tracker.
Also make your issue tracker for more than bugs. Make it usable for features too.
The advantage you have when building a tool like this is that you can "Eat Your Own Dog Food" and thus be your own user!
Might I ask why you're building "yet another" issue tracker? Whenever I think of a decent idea but find out there are already so many implementations, I reject it. Is that unwise?
Also make your issue tracker for more than bugs. Make it usable for features too.