Solomon Grundy and Clayface. I found him at Wal-Mart, but have already seen him at Target as well, so he's clearly not a retailer exclusive or anything. He shouldn't be too hard to find.
Like Solomon Grundy, Man-Bat has a button on his back to make his arms move (or in Man-Bat's case, 'flap.') Also like Solomon Grundy, Man-Bat can hold on to an average sized Imaginext figure with his 'hands.'
Man-Bat is nice and solid, his feet are large enough to support him and his wings in pretty much any pose. His arms have multiple points of articulation for many batty poses. I especially like how he can envelop a figure like those weird bat creatures in Beastmaster.