So I posted this in the Doctor preview but didn't get any response. I think Doctor/Squire with Familiar on the board is a little interesting.
If you have a 2/5 opening, buy Squire with 2C, discard 3E,2C,S, draw 5C. Buy Doctor with 5, shuffle 3E,2C,S into deck, turn over and trash two. The chance of one of those being a Squire is 1-(2/3) = 1/3. Then you get a Familiar in your discard pile, so your draw deck is 4 cards (copper/estate) and your discard pile is 5C, D, F. You then have a 1/7 chance of drawing Familiar on the third turn.
Well, considering you need 2/5 and not 5/2 for this, and it's only a 1/21 chance given the 2/5 opening, it's not all that likely. But it does let you play the Familiar on turn 3, which is neat. Plus, you've already trashed away one of your Estates and Coppers and can start naming Estate or Copper with Doctor. Seems like you'd be in a really sweet spot if it hit.
You can also do it with 4/3 opening, but then you cut your chance of trashing the squire in half. But that still lets you get a Familiar in your deck on Turn 3 1/6 of the time. Having a coin token from Baker of course makes this better.
If you miss trashing from Doctor's on-buy ability, you can still play Doctor to trash. To trash the Squire on turn 3, you'd have to draw the Doctor and have the Squire be cards 6, 7 or 8 in your reshuffle (draw 1st 5, reveal next 3). The number of ways to do this would be, (if you trashed two cards with Doctor previously), I think, 3/20. (Doctor must be in first 5 cards (1/2), Squire must be in last 5 cards (1/2), squire must be in first 3 of last 5 cards (3/5). So, 15%.
Now if you draw Doctor turn 3 but miss Squire, then you're screwed, because you know you'll be drawing Squire next turn. Or if you have $5 you can overpay $2 for Doctor and guarantee to trash the Squire, but then you'll have two Doctors.
Anyway, that's not all the possible cases, but I wonder how viable opening Doctor/Squire with Familiar is. You could do this for other attacks if you're unable to buy them in the opening, I guess, but it's probably better to just buy money and directly buy the attacks.