At my job, we use HeyTaco, a Slack bot. Every day you can give up to five tacos out by @mentioning somebody with a :taco: emoticon. If you answer a question or help somebody out, they will probably give you some tacos. The app keeps track of who gets the most tacos with leaderboards and the like. This has instilled a culture of helping others out on the team, by gamifying it and making it visible.