If you've never seen this card, it's probably because you've never played competitively. Really, just look at it's Pokebody. Just for that, you'd put this card into nearly any deck you can.
This card is really good, but it's not perfect. It only attacks okay on it's own. Mega Punch is a value attack at 40 output for only 1 energy. Ruthless Tail was a lot harder to pay for until Double Colorless Energy became an option. But in all seriousness, you wouldn't attack with this card unless you were forced to, and when it comes to that, it has a retreat cost of 3 to prevent an easy getaway. Thankfully, both Moonlight Stadium and Metagross from Unleashed give it some needed help. So does Flygon from Supreme Victors. In a deck that revolves around Flygon, Nidoqueen is a good tech, anyway.
The real reason you play this card is for it's Maternal Comfort PokeBody, which adds survivability to any high-HP pokemon. Good candidates are (but are far from limited to):
-Gengar, which retreats for free. A tag-team of Gengars is a frightening thing.
-Donphan, which already benefits from Exoskeleton to reduce it's damage by 20. It also mops up the residual damage from Earthquake.
-Flygon. Bulky already, and helps Nidoqueen retreat for free.
-Steel types that benefit from special Metal Energy. Except Dialga G lv X, for obvious reasons.
-Any deck that isn't a Shuppet-Donk, SP with Dialga G, or anything that for some odd reason or another would not benefit from having it's damage quickly melt away.
Now let's kill it. Thankfully, we have a gold standard: Dialga G lv X eliminates any benefit that Nidoqueen provides to the team, making it nearly worthless as anything besides an attacker, which it wasn't great at to begin with. Luxray GL lv X may not do much damage to it, but it can fish Nidoqueen up from the bench so a Gengar could Shadow Skip it, which isn't lethal unless either a Lake Boundary or Lucario GL is in play. Pokemon Reversal can be used instead of Luxray GL lv X if you're not rich and are feeling lucky.
It takes a high-damage pokemon to one-shot this card, and if that's not possible, it's ideal to do 70 damage each turn over the course of 2 turns, granted they don't retreat. When this card is played, it's expected that the other player have some retreat aid, and it helps to remove that aid however you can (Dialga G lv X if you have it, or play your own stadium to replace Moonlight Stadium). Your opponent does not want this card in the active spot, so bring it up there, then attack as hard as you can. The longer this card stays in play, the more effect it can have on the game.
Nidoqueen from Rising Rivals gets a score of 3.5 out of 5.
Overall, this card suffers most from the existence of Dialga G lv X. If it weren't for that one card seeing such heavy play, you would be seeing a lot more of Nidoqueen. And why not? I still see it played with nearly anything, so Dialga is apparently still not enough to discourage many from playing this card. Also, spread decks hate this card.