Mega Man X2/Heart Tanks

Overdrive Ostrich
Get Speed Burner, Leg Upgrade, and X-Buster Upgrade. Near the end of the stage, you see a Heart Tank sitting on spikes, Stand on where the spikes are (but don't touch it), charge up the Speed Burner, and the do the Air Dash, and get the Heart Tank. You will die after getting it.

Wire Sponge
At the beginning of the stage, climb up the left wall.

Wheel Gator
Get Speed Burner, Leg Upgrade, and X-Buster Upgrade. You will see a Heart Tank, but you cannot climb up the wall due to the spikes. Stand on the higher ledge, charge up the Speed Burner to the left, do the Air Dash, and get the Heart Tank.

Bubble Crab
Get Bubble Splash, and X-Buster Upgrade. While you see the fish-looking submarine for the first time, charge up the Bubble Splash, stand on a orange rocket platform, do the dash jump, and get the Heart Tank.

Flame Stag
When you see a lava erupting, quickly destroy the enemy to get the Heart Tank.

Morph Moth
Get Crystal Hunter. Freeze the disk-throwing enemy, use him as a platform, dash jump, climb up the wall, and get the Heart Tank.

Magna Centipede
Get Speed Burner, Leg Upgrade, and X-Buster Upgrade. Avoid touching the yellow lights. Stand on the ground between the turret, and the giant blocks, facing left, charge up the Speed Burner, do the Air Dash, and climb up the ceiling gap, and get the Heart Tank.

Crystal Snail
Get on the Robot Walker, fall in the gap, go to the left, do the dash jump, jump off the Robot Walker, and get the Heart Tank.