Most definatley, review moderator.
Every day, when I'm at the flash portal, any 5 that I watch and rate, I also review. I don't just review it, but whether or not I even give it a low score, I tell the artist where they need improvment, and where they are doing just fine. I also go through the reviews (that is, if it is saved, and not blammed) and mark any of the reviews accordingly. If it lists the pros and cons like I do, I mark it as helpful. If it says somethind like "lol, this is originals" I mark it as useless. And, if it says something like "omFg, go rape a blam and go f**k yourself in the process" I mark it as abusive. So, I am not only helping the flash, I am also helping the review space. I do this every day.
My second choice, icon moderator
Every now and then, I visit the iconhelpers page, watch a few flashes (I try to do at 10) and make a good icon that isn't a picture relevent to the name, but is a screenshot of a moment in the flash. (On my computer, I do this by pressing the print screen__sysrq button, then cropping out a section using MSpaint, then shrinking it to 46x46 and re-coloring if necessary). I see the number of how many flashes have icons and how many don't and personally, I think it's pretty disappointing. If I were an icon moderator, I would contribute a little bit of my time, every day, approving icons and shaping up the flashes.
My third choice (you probably could've guessed it), BBS moderator
It's not every day when I'm on the Forums, but whenever I'm done voting on 5 flashes, I quickly go to the BBS and see what's going on. Sometimes, I post on other people's posts, sometimes (not that often) I'll start my own thread. Whenever I do start a new thread, I always make sure the title is relevent, it is more than 5 words, and is not in all caps. When i go to other posts, if it is breaking any rules, I point them out like if it has already been done before, I post a link to the original post. If it is NSFW, I usually send the link to a moderator. I do my best to help out regulars and current moderators.
I am not posting here due to power hunger, I really think I can help out on newgrounds and I really want to see a difference in the reviews, icons, or BBS. Like Ghandi said, "You have to be the change you wish to see". Whenever I'm on newgrounds, on Mon-Thu (unless I have off from school on any of those days) I'm on for about 2-3 hours. But on any day I have off from school, I'll be on for hours on end.