Scamp is the name of several dogs owned by the Venture Family over the years.
Scamp 3 Edit
Scamp 3 was a dog owned by Rusty Venture when he was 8 years old. The Action Man, playing a trick on Rusty, threw a fake grenade. Unfortunately Scamp 3 ran up to it, and Rusty, fearing another death like Scamp 1 and Scamp 2, jumped on the grenade to save Scamp 3's life. The fake grenade, however, sprung a "boom" flag gag which pierced Rusty's kidney instead.
Scamp the Last Edit
The Scamp owned by Hank and Dean died and was buried by Brock Samson in his herb garden. This was kept from the boys until they found his collar trying to find the secret treasure there as hinted by the Rusty Venture cartoons.
It's possible this is the same Scamp that was seen in the pilot. Rusty removed the dog's skin and was using him to test cosmetics.