For tutor targets, one of the best is Unesh, Criosphinx Sovereign, which is sort of a hidden commander for the deck, supercharging all our sphinxes like Defiler of Dreams
The only time Ive ever gone after regular foils has been when they are the last to spike, the leftovers
For example, if you control The Ozolith ("Whenever a creature you control leaves the battlefield, if it had counters on it, put those counters on The Ozolith.") when Zack Fair's last ability resolves, you'll put the appropriate number of each kind of counter onto both The Ozolith and the target creature
Dice used must have equally likely outcomes and the roll must be fair
Copying a spell is a great way to counter a counterspell, or have a second removal spell, or just copy a card draw engine