Brian was showing David some neat shortcut key combinations in IntelliJ IDEA a moment ago. I jumped into the combination and asked Brian: "Close your eyes. And name five of your most often used IntelliJ IDEA shortcut key combinations." I didn't write down his answer, but here is my five favorite (not in the sense that I like them the most, but in the sense that when I close my eyes, these are the five that comes to my mind first because I use them regularly:
Control-n: find class
Control-q: quick Javadoc
Control-Alt-v: introduce variable
Shift-F6: rename
Control-Shift-Space: smart completion
Now that I think about it, I also use Alt-Enter a lot for intentional programming.