Gauntlet - for sure. That sucked loads of money out of me in the arcades down in the West County on family summer holidays back in the 1980s. My Mum even complained about it to me!
Xybots - Another multiplayers game which does require a lot of credits to get by!
Mercs - To continue or not continue? That is the question. To paraphrase the Bard.
I think I managed to get up to the level where the end of level baddie was the train with the guns! I did it on about 5 or 6 credits! After that, I though : "This is sucking me dry!"
Final Fight - Did suck a lot of credits out of me. I think that I managed to get to the second level - but that's all.
Aliens - Did seem to suck a lot out of me. Another multiplayers game(spot the connection). Managed to get to the second level again.
Smash TV - Now, this I did complete. I think I did use a few credits - but I did manage it with an old schoolfriend.
Streetfighter II - Took a lot out of me - in the day. I did progress, and eventually manage to finish the game on 1 credit. I think I did Ken, Ryu and Guile in the end. The ending scenes were cool to watch.