Goblin War Wagon 
Artifact Creature — Juggernaut
This creature doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {2}. If you do, untap this creature.
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Cards that do something similar expected a card that isn't here?
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Goblin Dirigible 99%
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"At the beginning of your upkeep, you may pay {4}. If you do, untap this creature."
+1 more matching line
Brass Man 98%
#25713
"At the beginning of your upkeep, you may pay {1}. If you do, untap this creature."
+1 more matching line
Brass Gnat 98%
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"At the beginning of your upkeep, you may pay {1}. If you do, untap this creature."
+1 more matching line
Mana Vault 87%
$113.72#145
"At the beginning of your upkeep, you may pay {4}. If you do, untap this artifact."
+1 more matching line
Island Fish Jasconius 85%
$0.33#26231
"At the beginning of your upkeep, you may pay {U}{U}{U}. If you do, untap this creature."
+1 more matching line
T-45 Power Armor 85%
$0.66#8517
"At the beginning of your upkeep, you may pay {E}. If you do, untap equipped creature, then put your choice of a menace, trample, or lifelink counter on it."
Dream Tides 83%
$0.44#17778
"At the beginning of each player's upkeep, that player may choose any number of tapped nongreen creatures they control and pay {2} for each creature chosen this way. If the player does, untap those creatures."
+1 more matching line
Magnetic Mountain 83%
$0.41#22770
"At the beginning of each player's upkeep, that player may choose any number of tapped blue creatures they control and pay {4} for each creature chosen this way. If the player does, untap those creatures."
+1 more matching line
Mudslide 81%
#19339
"At the beginning of each player's upkeep, that player may choose any number of tapped creatures without flying they control and pay {2} for each creature chosen this way. If the player does, untap those creatures."
+1 more matching line