It looks like you've got general use covered with the p3d, and the DBS is a thrower right? The MC-E is flood, so far so good.
Maybe an XP-G light might be good? Maybe the illuminati or the preon?
Or a headlamp?
Zebralights are always good
I think a quark might be a good choice too just because they are so versatile, having interchangeable parts. You could get a quark of you're choosing, a prism head and an extra body or two.
I guess the quad color mc-e light is interesting but to me it is just the flavor of the day, I see no use for it, especially one that would justify dropping 100 bucks on it.