For reel slots, the Blazing Sevens machines. They have relatively low progressive jackpots (a little over $1000) but seem to hit fairly often. I don't play slots much, but I see people hit the minor jackpots ($200-500) fairly often. But, they are usually $1 machines, 2 or 3 coins for full play, so they may not meet your criteria.
Or, Wild Cherries machines (Double, Triple) pay for Cherries in any reel position. Or any machine that pays for a symbol in any position.
Otherwise, I agree with tonyrob-video poker, single line $1 (which costs $5 per spin).
Don't forget to set down, preferably on paper, the terms of distribution before you start: How is any money won going to be distributed? 50/50 per every spin that results in a win? 50/50 on the total after the $600? Will you tell if you win and he isn't there? LOL.