Mega Man was used by one of the most popular "sprite comics", Bob and George. The author took the graphics from Mega Man and told his own stories with them. Although it started as a self-insert fanfic, it eventually weaves in some Mega Man lore as well. And then it inspired a lot of other sprite comics too! A lot. A lot. (The site even hosted many of them for a long time)
Lots of people will talk about how Mega Man 2's music is the best. I really love it, and also, I listened to a lot of OCRemixes. I would say A-Rival's are the ones that stuck with me the longest. (But there's so much to be said for the originals! And there's so much that has been already said about them!)
Isn't it cool how Mega Man has become a template for people to jam on, from its sprite art to its music and its gameplay? That's so rad!
In Mega Man 1 You can press Select repeatedly to pause and unpause, cancelling a boss' invincibily window after he gets hit.
In Mega Man 2, you can press Start to pause and shots will go through you!
I just think it's neat that these older games have some exploits that are pretty easy to do on your own. If you play through Mega Man X in suggested order every time, you might miss how stages change!
Mega Man Homepage: MMX Tricks:
Defeat Chill Penguin and Flame Mammoth's stage will freeze over, making some of the fire hazards a bit easier. Storm Eagle's demise wreaks Spark Mandrill's home, turning off the lights and introducing some new Spark hazards Destroy Launch Octopus and you will flood Sting Chameleon's forest. This makes some jumps a bit easier.
This gets used a few more times in X3. It's a really cool reward for defeating a boss but is also fairly rare. here's a blog someone wrote about it!