The Context: After ascending a communications tower with over 20 floors, Snake reaches the roof but is not out of danger yet; Liquid is in a Hind D prepared to "swat a bothersome fly". It's not exactly the most plot-relevant battle but certainly one of the most challenging in the game. Furthermore, no one can forget Snake's classic befuddled expression to Liquid having access to the chopper; "A Hind D!??" The Fight: Outside of having to nail the chopper with missile after missile you also have to pay attention to its movements and flying patterns. Liquid flies above, under, and all-around the communications tower and just generally a pain to keep track of. You may not notice this in the thick of it but the movements actually become more and more complex as the battle rages on, meaning it takes forever to get those last few missile hits in.
22. The Harrier Metal Gear Solid 2
The Context: After you neutralise the connecting bridge of the two Big Shell sectors, Solidus Snake makes his first formal appearance in the game. Not only does he destroy the bridge, but he and Vamp hop into a harrier and begin firing missiles at a grounded Raiden. The Fight: This is a battle very similar to the previously discussed Hind D fight but with more modern shooting mechanics and less frustrating camera angles. There's no denying that as a result this battle is easier, but it's also more memorable. Plus it's interesting that you can now fall off the battleground or hang off of the bridge's ledges to hide from the numerous missiles that the harrier fires at once. Modern conventions aren't the only reason this battle is placed just above the infamous Hind D though, as the cinematics before and after the fight are highly relevant to the plot.
21. Screaming Mantis Metal Gear Solid 4
The Context: As the game reaches its climax, Snake - and franchise veterans - receive a blast from the past with a Beast resembling what is arguably the most iconic boss fight in franchise history; Psycho Mantis. It's even peppered with nostalgic fourth wall-breaking jokes like Screaming Mantis trying to read the contents of your memory card - something that obviously doesn't exist for a PlayStation 3. The Fight: It's essentially a complete throwback to the original fight; Meryl will fall under mind control and begin attacking Snake unless she is put to sleep. Regular bullets are ineffective and the solution to winning the fight is bonkers; basically you have to shoot down possessed dolls hanging on strings that are attached to Mantis, grab them and use them against her, which in this case involves shaking the controller. It's truly one of the most unique fights in the franchise, but simply relies too much on nostalgia to place any higher.