Necro Gardna has been limited to one as of March 2010, however it's usefulness hasn't gone away. With field advantage being severely important and heavy hitters on the loose everywhere, Necro Gardna helps to give you a bit of a brace against these sort of things.

Necro Gardna fits best into decks that use discarding cards such as Phoenix Wing Wind Blast, Lightning Vortex, and Snipe Hunter. These cards are most commonly found in decks such as Volcanics, Light and Darkness Dragon decks, Zombies and sometimes even Blackwings. Notice that these decks thrive on field advantage. Necro Gardna makes a perfect fit in these kinds of decks as he puts pressure on the opponent and forces them to play around him. This gives you mental advantage. And if your opponent doesn't think about Necro Gardna he or she usually ends up making a crucial mistake(such as trying to go for an OTK only to be interrupted). Cards like Phoenix Wing Wind Blast and Lightning Vortex fit very easily in most rogue decks as most non-tier 1 decks focus on slowing the opponent down, which PWWB, Vortex, and Necro Gardna all do.

Other decks like Zombies not only run Wing Blast, but also cards like Armageddon Knight and Dark Grepher. These cards send monsters to the graveyard, of which Necro Gardna is a perfect candidate to be sent along with another monster such as Destiny Hero - Malicious or Plaguespreader Zombie. And of course, who can forget Lightsworn? That deck absolutely needs Necro Gardna, as Lightsworn does best the longer it can keep field advantage, and having your Lightsworn monsters protected by Necro Gardna can be a life-saver.

To sum it up: decks that discard a lot, send cards from the deck to the graveyard, and thrive on field advantage need to run Necro Gardna. Examples of these decks include Lightsworn, Light and Darkness Dragon, Volcanics, Zombies, and Dark Creator Turbo.