One from the arcade version of RoboCop 2, which I wrote all about last week.
This game was so popular in my local arcade I often had to queue to play it. There was something incredibly appealing about a side scrolling brawler where you had a gun all the time, instead of picking one up occasionally and running out of bullets. In this you could pick up another gun occasionally but it shot fireballs! Pretty revolutionary concept until Cadillacs & Dinosaurs came along which threw extra weapons at you like sweets instead of doling them out in a miserly fashion.