Having found a nice vector graphics for magic symbols, I wonder what the symbols on the second-to-last row are:
I recognize tap, untap, infinite and half, and the last one as the earlier white, but what are the others?
They are old versions of the tap symbol.
As it is explained in this article posted on Daily MTG, the symbol with the T is the tap symbol from Revised through Fallen Empires and the one with the rectangle is the tap symbol from 4th Edition through Scourge.
The article includes an image with old versions of Royal Assassin making it pretty intuitive that they're tap symbols: