Couldn't find this already posted.
AVIS Preferred sent me a link to the AVIS Advent daily draw.
Prizes vary but include upgrade vouchers, free rentals, etc.
Hope it helps someone.
"Bursting full of the finest Christmas treats from Avis - including free Prestige car hire, weekend stays at top Hilton hotels, DSLR cameras, luxury luggage and a BA holiday worth £5,000. There is something magical to win everyday from the 8th until 19th December. Just solve our daily rhyming riddle, to unlock the prize windows."