Its a scam.  If you talk to them they'll ask for a bank account number or credit card number to pay for shipping and handling.  They will spend all of the money in the account.  They will never send you a gift card.

thank u for choosing me

"We have selected you in our giveaway for a FREE WAL-MART Gift Voucher worth $1000 - Please visit http://www.free-gift-offer.com (#ESC#2REMOVE)"

Funny... I figured that if I had won something from Wal-Mart, I would have probably been directed through a Wal-Mart website instead of some generic nonsense that looks like something out of the back of a Cheaper Than Dirt magazine. I guess some ratty little (illegitimate children) in North Vegas thought they could scam  back the money they threw away at the roulette table.