Is Prowess and Storm on the list that you intended to keep or prevent? Because it's not very easily deduced. The long and short of it is that lands don't belong on the stack, and you should do your best to not do something that would imply they end up there.@Mown
The reason why I used the card as written was to keep or prevent certain triggers from firing (Prowess, Storm, Landfall etc.) and also because I think these are kind of ugly (well, the instant is cute), but it may not be worth the effort. Actually, these triggers might be beneficial, not something to reign in. What do you think? I thought that getting to surprise someone with an extra land would be enough benefit, but maybe not.
Is Prowess and Storm on the list that you intended to keep or prevent? Because it's not very easily deduced.
The green and the white ones are broken (as in too powerful), the blue and the red ones are broken (as in they can't work by the rules), the black one seems very cool. Well, they all are pretty out of the box ideas, so you get a lot of cool points, but I think some of these need tweaking
Some suggestions (in WUBRG order)
Oh, by the way, nonbasic typed lands have a reminder text to indicate what they tap for. See Idyllic Grange and Mistveil Plains, for example.
Alright, back to the suggestions. They might or not might be up your alley, but I tried to riff on your ideas a bit
Cradle of Civilization
Land - Plains
: Add . Activate this ability only if you attacked with three or more creatures this turn.
Land - Island
Whenever an opponent plays a land, you may reveal ~ from your hand. Put it onto the battlefield if you revealed no other cards named ~ from your hand this turn. You can't play land cards during your next turn.
Land - Swamp
Morbid -- You may play ~ from your graveyard if a creature died this turn.
Cliffs of Insanity
Land - Mountain
When you discard ~, add . Spend this mana only to cast artifact or creature spells.
Land - Forest
At the beginning of your upkeep, sacrifice a Human. If you do, create a tapped Forest land token.