This is key if you want to build around this with themes that let you tap your creatures, like vehicles and mounts
Concealed Courtyard, Spirebluff Canal, Blooming Marsh, Inspiring Vantage and Botanical Sanctum reprint MTGs offering of enemy fast lands - land cards that can be tapped for either of two mana colours, but enter the battlefield tapped unless you control two or fewer other lands
Vindicate Obviously Vindicate at number one, one of the greatest ever gold spells
For example, if you somehow control two copies of Zopandrel, a 2/2 Bear Cub becomes a 4/4 creature when the first ability resolves and then becomes an 8/8 creature when the second one resolves
You could get Gaea's Cradle if your deck cares about creatures for a few mana
Do you know what else is one-of-a-kind