Right now, the US Club Nintendo is offering up four digital rewards for 150 coins each. Kid Icarus (3DS eShop), Starship Defense (3DS eShop), Super Punch Out!! (Wii Virtual Console), and Mario Tennis (Wii Virtual Console) are all up for grabs. On April 7th, Nintendo will shuffle their rewards around, and the aforementioned games will be gone.
Personally, I think all of these games are solid, but Super Punch Out!! is an instant recommendation if you've never played it. It's easily my favorite Punch Out!! game, and one of my top Super Nintendo titles of all time.