Okay, this doesn't include structure deck re-prints because that would be just plain stupid and I might as well be calling them they rarer old ones:

10-Upstart Goblin- So what if they get 1000 lifepoints? You get to draw, and if you run Bad Reaction to Simochi for a combo, you instead dealt them 1000! Nice? Perhaps.
9-Vindictive Old Fart(Magician)- Come on, Man-Eater Bug was a Super Rare!(In packs)
8-Giant Orc- So there's the attack force; Can you say budget deck?
7-Thunder of Ruler- This thing is as good as Waboku, just not chainable, good for the desperate player and definitely nice in Limited since usually m/t destruction isn't too rampant.
6-Sakuretsu Armor-So what if it kills only one monster? It's way cheaper than an Exiled Force or Mirror Force, more budget deck usage here.
5-Waboku- Not necessarily underrated, but some people will call you a newb for using one.
4-Bait Doll- Perfect replacement for MST, most smart people won't set a Magic(Not Spell) card unless it's for a good reason.
3-Magical Marrionette-As big attention as this card got, I never see it, even with the Butterfly Dagger combo, situational, but still good on it's own. Unlimited attack if you can get that high, baby!
2-Great Maju De Eiza(Think it's right..)- With Chaos Decks and removal running around now, WHY NOT?!
1-Bum bum buuuuuuuuuuuuuuuuuum! And the prize goes to....!
A Hero Emerges- ::Smack:: Hello!? A free Monster from the hand? What happens if you're tribute screwed with a 2 BEWD and you draw that hero emerging? Sound good? Thought so.