I already commented on a crash bug #785

I've also seen "phantom block placing" where I place a block and it promptly disappears. Confused, I saved & quit and restarted and low and behold my hotbar slot was empty, but while it was exhibiting the bug it showed 50 or so blocks available to place. This happened after I was doing a backward run placing dirt blocks as fast I could without them double stacking.

Finally, if a tool breaks and there is no replacement for some reason it grabs the stack of cobble I keep in hotbar slot 5 and sticks into my hand.