Coast Gateway Hotel (18415 International Blvd, SeaTac, WA 98188) is also within walking distance (at least for me). Added benefit: Right next to Sharp's RoastHouse, which gives you a coupon for free BBQ nachos or creamer potatoes. I'm a fan of their Bourbon flight.

Absolute shortest walking distance, though, already mentioned, is the Radisson Hotel (18118 International Blvd, Seattle, WA 98188). It's next to the 13 Coins SeaTac restaurant, which also isn't terrible.