Playing Megaman X 1 and being a badass about it. The only upgrade I got before Sigmas fortress was the mandatory legs upgrade, and I got it right away.
Boss observations:
Chill Penguin: Goes down like a chump.
Storm Eagle: Goes down like a speedy chump.
Spark Mandril: Sometimes a little tricky but once you know his pattern he's easy.
Armored Armadillo: **** THIS GUY. It's not that the fight is that hard, it's just that it's so damned long because he only takes 1 damage no matter the charge level of your gun and you have to get him to pulse his armor in order to get another shot on him while he's on the ground.
Sting Chameleon: This one can be tricky, but as long as you avoid his tongue attack it's not that bad.
Boomer Qwuanger(sp?): Just stick to the walls and wait out his teleporting phases, then drop down and blast him. Easy.
Launch Octopus: The only real danger is when he launches his 4 huge missiles at once. Good chance he will also jump when you bounce off the wall to dodge. Can otherwise just shoot his regular missiles down with rapid fire buster shots.
Flame Mammoth: Goes down like an overweight chump.
Vile: No walls means you gotta be fast on the ground and dodge everything. Kinda hard fight.
Bosspider: Not that hard if you can figure out its path along the vines.
Rangda Bangda: Sticking to the walls helps. Long fight, but not too technically difficult:
Ugly Demon Car Thing that I don't know the name of: Well so far this is the only boss that's got me stumped. Ugly piece of ****.
I'm anticipating that only Sigma's final form will be any challenge in the last stage. Three bosses with only 16hp, no armor, and no subtanks. Gonna be a fun fight.