customer list (tech interface) with customer login (frontend) (username & password)
Calendar with e-mail/sms function (being capable of setting when to send the reminder)
Knowledgebase
Self Help Wizards
News (haven't found that if it already is in the system)
More skins included by default
More languages included by default
Quick replies
Subtopics
payment system (to keep track if a customer paid his bill (has to be entered manually))
time tracking (how long is the rep working on the case)
time billing (Bill the customer for the time the rep has been working on the case)
merge tickets/split tickets