Assault/ Assault Plus - Very underrated twin stick shooter for arcades. One of the most graphically impressive games of 1988, and contains a ton of replayability thanks to responsive controls, a large amount of stages, and experimenting with different paths. Plus version also adds a easy/super mode with altered level layouts. Sadly ahead of its time, and never got any sequels.
Armored Warriors- Nice arcade beat-em-up with good graphics due to cps2 hardware, the ability to customize your weapon/arm/leg system from defeated enemies, and a high difficulty especially in the last few stages makes this a decent challenge for a 1cc (in my opinion). Kind of a crime that its sequel ended up being a 1v1 fighter that got mostly ignored in arcades.
Front Mission 2- Second entry in the series, that contains a ton of upgrades compared to the first games with the Action Points system, along with a mature storyline and a high difficulty to boot ( got stuck near one of the super tank missions about 60% in). Unfortunately, due to the mature content, Square never released this in the US and the only way to play is to find the translation patch for the game ( which also requires a gamefaqs script for the last 30% of the game).
Some other ones I can reccomend are Dogyuun, Bangai-O Spirits, Granada, Hyper Duel, Super Robot Wars F Final, along with Gundam Battle Assault 1 & 2. Would like to add Metal Wolf Chaos once I have access to it via softmod.