Well, there's always the famous/infamous Rise Up Singing if you know enough tunes (no tunes included).

Do you use a capo? If not, I'd encourage you to get one and use it, since then you can play hundreds MORE songs with just those chords, since you can change keys without having to learn more chord patterns. Also, if you play for a long time, playing C and G over and over again is sometimes less stressful on the left hand (on my left hand, at least) than scrunching up for D and A, and you'll get to use more strings on those chords.