Misc. Other Stuff
These may or may not be useful, but they are known.
Bolt Duplication
One of the bolts in Sword Man’s stage can be duplicated. This is useful in 40 Bolts (which is essentially the 100% category for this game). A video documenting this can be seen Here - https://www.youtube.com/watch?v=bCRThMDP79o
Rush Bike Double Jumps
When you take damage while riding Rush Bike, there is a one frame window where you are grounded and can jump after regaining control. This would save time in RTA (for example, riding the bike to the boss door in Grenade), but it is too precise to do and there is currently no setup to do this anywhere in RTA. You can see a video of this trick in action here - https://www.youtube.com/watch?v=LhbWBU32lNg.
Infinite Sword Glitch
Destroying a slime enemy with Flame Sword and getting grabbed on the same frame will spawn a permanent Flame Sword hitbox in front of Mega Man. Taking any sort of damage or using Flame Sword again will cancel the effect. This is currently not useful for RTA, but you can see a video of the glitch here - https://www.youtube.com/watch?v=XLyMGS1ZBIY.