Speaker events. IT security best practices. The perks of working at an internal agency. But seriously, these projects can be a blast if your designer is willing to spend undue amounts of time brainstorming.
I created this spec work in college. My team created the Burrito Friends Forever loyalty program to drive traffic among people ages 15 to 25. The reason I keep this spec work around is because while the BFF program was the combined effort of my group, these ads, these ads were all me.