The Gog Summer (Winter) sale has already been mentioned on Ozbargain, but the sale items haven't been itemized or updated, so I just wanted to let people know about some of today's better specials. I recommended perusing GOG once or twice a day since the sales only last 24 hours. Perhaps there will be a finale at the end, but there are no guarantees.
Door Kickers $5 US (75% off) http://www.gog.com/game/door_kickers
Shadowgate $2.29 (85% off) http://www.gog.com/game/shadowgate (Groupees has a Bundle of adventure games that includes a Steam key for Shadowgate for $4: https://groupees.com/bm20/
Shadow Warrior (the 2013 release, but the ancient 2.5D Build engine game) $4 (90% off) http://www.gog.com/game/shadow_warrior
Oldies on sale I also recommend (from personal experience or reviews): Port Royale, Advent Rising, Stronghold Crusader, Clarc, TA Kingdoms, I Have No Mouth, Commandos, Sacred 1 & 2, Inquisitor, Eliminage Gothic, Sea Dogs, Master of Magic, Blazblue Calamity, Commandos, Evil Genius, Undying, Tales Maj'Eyal, Defenders Quest, IL-2 Sturmovik, Celtic Kings, Silent Storm and Soulbringer.