This is announced, but I guess many people do not read the news post twice:
Many Devolver Digital games are added to the sale.

RWarehall just provided a full list:
https://www.gog.com/forum/general/the_st_patricks_day_sale_begins_on_gogcom_26259/post160

Vaporum
and
Tower 57
are just added to St. Patrick's Hats.

Plus Daedalic's catalog, according to the news update.

Hmmm... should I press my luck on the off chance of snatching Shadow Tactics: Blades of the Shogun? :P

Definitely is not in the Leprechaun Hats. I do not own it, and I already know the titles in the Hats I do not own.

Daedalic's catalog are added to sale, but I am sure some of them does not added to the Hats.

Another good news:
Discount of Ruiner just changed to 50% off (from 33% off previously).

Some games just silently added to the Weekly Sale:
https://www.gog.com/promo/20180319_weekly_sale

Outcast - Second Contact
Furi
Furi - One More Fight
Furi Original Soundtrack

50% off Battle Brothers

Freedom Planet silently added to the Weekly Sale.

GOG silently adjusted the discount of The Curse of Monkey Island™:
25% off -> 36% off
(You must have both Special Edition of Monkey Island 1 & 2)

I bought The Curse of Monkey Island™ at $5.24(6.99),
but you can get it at $4.50(6.99).

UPDATE
GOG silently adjusted the discount of both Special Edition:
60% off -> 65% off

GOG's internal workflow is soooooooooooooooo bad,
and their countdown clocks of Weekly Sale is still wrong.

GOG provides refund for the discount change, please see:
https://www.gog.com/forum/general/release_the_curse_of_monkey_island_maniac_mansion_a2bf2/post170

UPDATE
I got my refund for the $5.24 -> $4.50 issue.

GOG's discount system is inconsistent again.
Select all 3 games in the Monkey Island Special Promo: $10.48
BUY SERIES discount for all 3 games above: $13.97

If you bought Monkey Island games with a higher price, do not forget to contact GOG Support and get a refund.

50% off Banner Saga series

GOG silently added some games to latest Weekly Sale:
https://www.gog.com/promo/20180326_weekly_sale

Below games were not in the sale initially:
Catacombs Pack
Symphony
Hot Tin Roof: The Cat That Wore A Fedora
Smugglers V
Smuggler's Guild
Smugglers V: Incasion
Rebuild 3: Gangs of Deadsville
Incredipede

If you want to buy 140 and its Soundtrack,
This sale is cheaper (10 hours left):
https://www.gog.com/promo/20180319_weekly_sale

GOG silently added some games to latest Weekly Sale:
https://www.gog.com/promo/20180326_weekly_sale

Headlander
Headlander + Soundtrack
Rain World
Kingsway
Battle Chef Brigade