This app was mentioned in 2 comments, with an average of 2.50 upvotes
Most of the time, I use 6-4-3 (full disclosure: I made this app) on my phone. For paper, though, I do have both Eephus League books. They're great!
Sorry about the delay in getting back. Been moving into my mansion this weekend. ;)
Seriously, I've been very fortunate. The app is rather niche. It's the 6-4-3 Baseball Scorecard. For those unfamiliar with baseball scorekeeping, there is a notation (with a great many personalized variations) for recording the events of a baseball game. This is done for an official record and stat compilation, but also done recreationally by many fans as a way to enjoy the game more. The app is designed to be suitable for either purpose. In addition to producing nice clean scorecards that can be shared via social media, it also does stat tabulation, saving youth coaches, reporters, and even MiLB staff hours of paper-and-pencil time after games are over.
The app is a straight-up purchase. No ads, no in-app purchases. It is at the higher end of the spectrum, launching for $9.99 in 2010 and then coming down to $7.99 last spring. The rationale for the high pricing was that I was very fortunate to be the first one into the market for Android. Two other big players were already out on iOS. One app was free but then had a subscription service, and the other was priced at $10. I figured being the only game in town for Android, I could command the $10 price point, too, and it worked out pretty okay.
Sales have definitely dropped off in the last couple of years. We had a second kid, and time to work on it has dramatically fallen off. Meanwhile, one of those two major iOS apps came to Android with a full staff of developers doing it as their primary job (and, at least for a time, the backing of ESPN) and has emerged as the dominant app, but I'm cool with that. Honestly, the project started for me so I could score the game on my phone when I went to the ballpark, and if nobody else ever used it, I was okay with that. As it turns out, I have a solid user base from whom I've received some wonderful letters over the years, and there are specific reasons some people prefer my approach over that of the other app.
I don't have to be the biggest app in that space. I'm just tickled that a substantial number of people think I'm the best.