I've been a fan of the Homerun Battle series since the first (originally titled Baseball Slugger) title, Homerun Battle 3D [$0.99], launched in early 2010. Nearly two years later, Homerun Battle 2 [$0.99] hit, and while it's a little more IAP-oriented than I'd like it to be, it still retains all the fun instant online match ups of the original.
Anyway, starting this week Homerun Battle 2 is going to behaving weekly competitions. For an hour every Friday starting at noon Pacific time (So, 1:00 Mountain, 2:00 Central, 3:00 Eastern) if you beat a Com2uS employee you'll win $5 worth of the IAP currency. It sounds like all you've got to do is add the user "com2ususa1" to your friends list and spam them with challenges. Also, during this time there should be tons of normal players on to play with while you wait to jockey for your free in-game currency.
Win or lose, it's a good excuse to re-install the game if you haven't played in a while. I've always kept Homerun Battle 2 on my phone as it really caters to that whole "I feel like playing something and have exactly 45 seconds to do it" niche that mobile games fit into so well.
Oh, and there's also Homerun Battle 2 Free [Free] if you want to fiddle with the game without any kind of financial obligation.