[BullDog]

This spring I cleaned out the gutter, and found all kinds of things growing in there. I thought this guy was pretty cute, so scooped it up with some gutter junk, and stuck it in a 2" pot. It's just gone nuts! It's close to 2 feet tall now. I was going to stick it in a bigger pot, but I was wondering if anyone could take a guess at what it might be?

Leaf closeup

 

[neven]

Amur Maple??

 

[BullDog]

In my googling, Amur Maple definitely came up, though this guy doesn't have as dark of leaves as some of the pictures I found. But that could be because it's young.
I also found Acer crataegifolium/Uri Maple, which has similar leaves...

 

[plantedinvertz]

We have a similar looking plant in our yard....

 

[Ursus sapien]

looks like an acer seedling