Gen 1 Game Corner:

 Machines enter a "golden state" sometimes where you will win 90% of the time, giving you 300+ coins by the time it dissipates.

Problem: no idea what triggers the state. Best guess is random. Machine below broken machine may have best odds, but need to leave Game Corner and go back in to reset it. 

Don't care. Game Corner a desperation resource for Nuzlocke runs only, and have wasted enough time on it already.

I blame nostalgia.

Pokemon Blue Nuzlocke Time! (Part 7)

( All of Vermilion City, including S.S. Anne, Lt. Surge, and both routes leading out of the city, is beneath the cut! )

Pokemon Blue Nuzlocke Time! (Part 8)

( Rock Tunnel! Go go go! (As a bonus: without using Flash! :D) )