OK, this is a little last minute, but I was out until now. Since I'm posting this so late this may only help west coast people, or possibly even east coast people if you order online.
Today (6/26/16) seems to be a confluence of promos and discounts, so that it's the "perfect storm" of offers. For today only (because some promos end today while others just started today), you can maximize some discounts and promos.
After today, you can still get most of the promos, but not all of them.
Eligibility:
-I think some of these promos are only for AT&T customers (either new, or existing). Some may also be for those with other carriers, but you have to check. I know all of these are eligible with AT&T.
-If you are an existing customer, I think you have to upgrade or add lines on your account. If you are not upgrade eligible and/or you don't want to add a line to your account, you can't take advantage of the BOGO (but you should be able to take advantage of the other promos).
Promos:
(AT&T): BOGO. If you buy a Samsung phone (I know the S7's are eligible, not sure about other phones), you get another for free. [Show spoiler]Rep told me up to a $595 value, but I think I read somewhere it was up to $695; if the former, then technically you will still end up paying about $100 for the second phone if you get 2 S7's. Obviously, this is only useful if you are going to be getting 2 phones. I think to be eligible for this you have to upgrade and/or add new lines to your account. Works out as a reimbursement and statement credit after up to 3 full billing cycles (you may have to pay 3 months of installments on the phone before being reimbursed and getting the credits for the BOGO). Just pay taxes day of purchase.
(BOGO Expires 6/30).
(BB): Free $100 GC with Samsung Galaxy phone. [Show spoiler]I think the $100 GC offer may also apply to other phones, but S7 is definitely included. If you get 2 phones (using the BOGO), you still get 2 x $100 GCs (so $200 total) even though one of those phones will essentially be free.
($100 GC offer possibly expires 7/2/16 or maybe 7/10/16, not exactly clear when this expires).
(Samsung): Free Gear VR virtual reality headset. [Show spoiler]Free with purchase of each Samsung S7. Again, if you get 2 S7 phones, you will get one for each phone.
(Expires 6/26/16 TODAY! This is really the one that you will miss out on if you don't order today. All the other promos extend beyond today, I believe. So, even if you don't get an order in today, if you are interested in the other promos, you still have at least until 6/30/16, when the AT&T BOGO deal ends).
(Samsung?): Free Wireless Charger. [Show spoiler]Free with purchase of S7.
(Not sure when this expires, but probably good through at least 7/2/16, the end of the week).
(AT&T): G2 Smartwatch for $0.99 (or Classic version for $50). (OK, so not exactly free for the basic version, but under a buck!).
[Show spoiler]
Note 1: this requires a 2 year contract on the watch (and also I think the phone). [Show spoiler]The watch 2 year contract is for the $10/month data fee that you need to get for the watch to be able to utilize the standalone data and call features (i.e. when your paired phone is not nearby). After the 2 year contract is up, you can stop the $10/month data and just pair your watch to your phone exclusively via BT, but then that requires that the phone be near the watch (within BT range) to be able to access the data and call features of the watch. With the $10/month watch data plan, you can access data and call features on the watch even if your phone is not nearby. You need to pair it with a compatible Android phone.
Note 2: This was a really frustrating promo because it seems they make it nearly impossible for you to actually get this free promo easily. [Show spoiler]Since the watch is (like) a cell phone in that it actually has a designated number assigned to it, it must be purchased there in the store when you are buying your phones, meaning it has to be in stock in the store you are buying the phones from. However, this doesn't seem to be merely a matter of inventory since my store said that none of the stores in my area actually carry this product, they can only order it into the store (or to your house) for you. Possibly some stores in certain areas (maybe big metro areas) may carry this phone in store normally, but all the ones in my area apparently do not. They said you could potentially order the watch in, then when it arrives return everything and then rebuy everything again, this time with the watch included, but they said that not only was this a huge hassle in and of itself, but it was further exacerbated by the fact that once you return the phones it apparently typically takes AT&T 1-3 days to make your number eligible for an upgrade again (since you won't be since their system just thinks you got a new phone and it doesn't automatically/instantly take into account that you just returned that new phone). Suffice it to say, and this is in the words of the BB and Samsung reps that I spoke with in the store, that AT&T sometimes has very frustrating promos that are almost impossible to actually take advantage of, at least in certain regions due to the fact that some products at are part of such promos are normally not carried in the stores. 
Anyway, if you can get this deal, it's yet another deal you can potentially get. If anyone wants this but your store doesn't carry this, one option might be to order the watch to the store first, and then go to the store to order the phone and other goodies after the watch comes in. Then, presumably you could return the watch, and then rebuy it along with the phone and other stuff so that they can be on the same transaction. I think the reps at my store indicated that that might work.
(Not sure when this expires, probably lasts at least until end of week, 7/2/16).
(BB): Free $25 RZ cert for every line after the first that you add to an account. [Show spoiler]So, first line doesn't count, but after that $25 RZ cert for each additional line.
(No known expiry).
So, I just got my parents 2 S7s, upgrading their currently S4s. I waited until today (instead of doing this yesterday) in order to get the free wireless chargers too. So we got everything (BOGO for the 2 phones, 2 x $100 GCs, 2 x Gear VRs, 2 x wireless chargers, 1 x $25 RZ cert), except the $0.99 G2 Smartwatches.
The only thing I couldn't get was the S2 smartwatch, due to the issues with that promo I mentioned above (we would've have gotten one of those if we could).
Still, overall, a lot of great, stackable promos for buying the Samsung S7s today. Today is the last day of the Gear VR promo. I think you can still do this online, so even east coast people could still do this. All the other promos should last at least until 6/30/16 when the AT&T BOGO deal ends. After that the other promos should last at least until the end of the week (7/2/16), possibly longer. So, if you only want to get 1 phone, you can still get the $100 GC, wireless charger, and S2 smartwatch (if your store carries it).