OK, I have a tough one. It's a really old two-player freeware DOS game that's kind of similar to Scorched Earth, but simpler. I played it in 1995 or 1996, but it might have been older than that... I think my dad found it on a BBS somewhere.
Anyway, it took place on a single screen, with a ravine roughly shaped like a V. Each player had 5 tanks on their side of the ravine. The tanks could not move. On your turn you selected which tank you wanted to use to shoot with, and then you picked one of three weapons. First was a grenade launcher that shot in a parabola. To use it, you had to pick the direction of fire first. This involved a little radar-like icon with a spinning arrow in it, and you hit a button to stop it when it was pointing in the direction you wanted to shoot. Then you had to choose the grenade's velocity, by stopping a bar as it moved up and down. The second weapon was a laser beam, which you just had to pick the direction of fire for. You could bounce the laser beam off the ceiling and back down onto the enemy tanks.
Lastly, there was this missile you could launch. This was the most complicated, as you had to pick a direction, a fire velocity, and also how much fuel you wanted, as it was rocket-powered. Also, once if was launched, you could remote-detonate it. For maximum damage, you had to remote detonate it just BEFORE it hit an enemy tank, so you timed the explosion correctly.
Explosions involved slowly filling up a circular region with red and orange pixels. There may have also been "smoke" pixels shooting out the top of the explosions. There were also some buildings scattered across the landscape that could be destroyed, but this was just for show. The game speed was tied to the processor so when my parents got a new computer, I couldn't play it anymore because it ran way too fast. On slow computers, the explosions could take almost a minute to finish rendering.
Ring any bells for anyone?
EDIT:
I thought of another game I can't remember the name of. I'm pretty sure it was for Sega Genesis, and basically it was a graphical roguelike. You started the game in a village, which worked a lot like a standard RPG village (like in Final Fantasy or something) where you would walk around in a top-down perspective and talk to people. Eventually you entered the dungeon, which was randomly-generated, and you wandered through rooms and corridors and walked into enemies in a turn-based fashion to fight. This was still from a top-down perspective, or actually more like an angled-top down. Not isometric, because it wasn't diagonal, just angled slightly off of purely top-down. If you took too long, all the enemies on the level would respawn. You found new weapons a lot. Anyone know that one? I remember that some enemies were ninjas, and sometimes enemies were invisible, or there would be a sword on the floor and you'd go to grab it but it would turn out to be a flying sword you had to fight. Also sometimes a level would just be a huge open room full of enemies and items.
EDIT AGAIN:
The Sega Genesis roguelike is
http://en.wikipedia.org/wiki/Fatal_Labyrinth. Still don't know what the other one is though.