For under $500 you can't beat a Savage, they are affordable and accurate, not much to look at but they will definitely get you in the game. As for caliber, if you want to have a rifle that will kill deer and hogs and not completely evaporate varmints then .243 would be a good choice. If you want to evaporate varmints then go with .308, .270, 30-06, the options are limitless.