Since you're in the PHP forum, I'll say PHP/MySql happens to be a suitable platform for a help desk application.
You could develop a system where user's can register and log in to report technical issues to different departments and your system can help route that problem to the appropiate department(UNIX, WINDOWS, SOFTWARE, HARDWARE etc)
Once the problem is corrected you can create a trigger in the DBMS that will notify the user via email . This is just a premise I think you could consider for your proj. Iam sure you can customize it to fit your sr. proj base on staffing and other issues.
dude maybe this is the hardest question u could ever meet
i faced the same problem with my gra project!!
anyway th best idea is the one u come with in ur mind ;)
so just look around and find what u need more
why dont you design something 'new' rather than just proving your skillsm ,ame something useful that you could use after university yourself or maybe try patent (although your uni will own some pf the IP rights)
I designed my own meal planning system (which i didnt end up getting patented cos it turned out there was something similar) but becuase it was entirely my own idea im sure i scored extra points and also you have the freedom to make it do whatever you want, rather than re-using some ideas someone else came up with!
Im not sure where your from, but i know in the UK there were quite a few more jobs in ASP than PHP. so it might be worthwhile considering the job market and what skills you think will get you a good job when you finish your studies, becuase you may end up a whiz in a particular language, but if theres lots more jobs in a different one you will be kicking your self!
I only just graduated last summer and realised all this once it was already too late!