Can you tap arbor elf to untap a forest to tap that same forest for an extra mana for the same mana cost of 1 card?! Phew...that's a big sentence
You may tap the forest untapped by {Arbor Elf} for an additional mana.
I do see why not
Tap forest.
One green mana in mana pool,
Tap arbor elf, untap forest
Forest again, now 2 green mana floating
to be used at anytime in the turn this happens,
If I'm understanding your question correctly, yes.
Say you have 1 forest and 1 {Arbor Elf} in play. You may tap the forest for mana, adding {G} to your mana pool. Then, you can tap the arbor elf to untap the same forest, and tap the forest for {G} again. You now have {G}{G} in your mana pool, and can cast a spell like {Strangleroot Geist} with it!
Just remember that mana empties your pool as phases and turns end/change, so you will have to use this mana before you change to the next phase or it will be wasted away!
RESOLVED
Thanks guys...my friend chase sucks...
Thank you garzo for correcting my little mistake,
You can also use {Arbor Elf} to untap a shock land with a forest in the land type. You could tap {Temple Garden} to add 1 {g} then tap arbor elf to untap temple garden then tap temple garden again for {w}