The DianSheng 10CM 3x3x3 is the largest 3x3x3 speedcube currently mass produced that has the potential for actual fingertricks, larger cubes (such as the 19 and 35CM cubes made by DianSheng) require the whole hand to make any turn. DianSheng have done an excellent job making this cube as it is magnetic, has an adjustment system and turns like a normal speedcube, it just happens to be significantly bigger than normal.

You can buy it here