I want to mention a game that had its own thread on this forum briefly: Bot Vice.
viewtopic.php?f=1&t=61115
I picked this up for $2 and I must say, it is surprisingly high-quality. The density of enemy and firing patterns, the silky-smooth control over your own character, and just how good the game feels to play should be commended. The game is brutally hard too. Unless you are a god gamer, you will get bodied pretty much from the very first level.
In gameplay, it's somewhere between cabal-like and light gun. You can take cover like in a Light Gun game, but you move freely and have a dodge roll like Wild Guns. You can slash enemies that get too close, as in Sin and Punishment. The game doesn't use free aim. Instead, you can either fire straight forward or hit a button to lock on to the nearest enemy. Some enemies are better taken with lock-on and others are easier to kill when firing forward. Your police gal feels incredibly fun to control. Your default pea shooter fires fast, the dodge roll has generous i-frames and everything explodes real nice.
I think BIL in particular would enjoy this game, given his penchant for a) difficult games and b) EXTREME CARNAGE.
As the other thread says, very little discussion of this game is to be found online anywhere.
I did find this non-english speedrun of the game, so if you're interested, check out the
MASSIVE EXPLOSIONS here:
https://www.youtube.com/watch?v=Mg28feGsyPM
My only major criticism of the game is I don't see a pure arcade mode. You have to select on level-by-level basis.