Most played cards in Urza:

1 Decks
Snow-Covered Island
6 copies - 6 average
Whir of Invention
4 copies - 4 average
Lantern of Insight
4 copies - 4 average
Pithing Needle
4 copies - 4 average
Leyline of the Void
4 copies - 4 average
Codex Shredder
4 copies - 4 average
Grafdigger's Cage
4 copies - 4 average
Mox Opal
3 copies - 3 average
Wasteland
3 copies - 3 average
Welding Jar
3 copies - 3 average
Defense Grid
2 copies - 2 average
Ensnaring Bridge
2 copies - 2 average
Urza, Lord High Artificer
2 copies - 2 average
Padeem, Consul of Innovation
2 copies - 2 average
Sol Ring
1 copies - 1 average
Pyxis of Pandemonium
1 copies - 1 average
Mystic Forge
1 copies - 1 average
Mox Ruby
1 copies - 1 average
Mox Sapphire
1 copies - 1 average
Ipnu Rivulet
1 copies - 1 average