Mine are in order:
1) Act 1 bit before you meet Otacon and Mk II
2) Bike chase - act 3
3) Beginning of act 2 - hillside steps
4) Crying wolf
5) Liquid ocelot fight at the end

I did not find the end battle to difficult.

I hated the bit in the boat though, I literally just could not figure out how to get through, It probably took me over 10 goes, in the end I took all the high ground, and resorted to using the mk2 just incase.

The only part I found difficult (more frustrating though) was the final fight with Liquid Ocelot at the end. It lasted too long and was boring as hell. The game is not a fighter and that section really proved it.

Crying Wolf was easy. Hide under tank, equip sniper and thermal goggles and she can't hurt you. No-one can.

I thought Metal Gear Solid 4 was pretty easy, I did die a bit but the only really hard part was Act 5. But just get the rail gun and kill the Gekkos.

Once you get the rail gun, nothing is difficult.

You can't use the rail gun when going for the BBE

Act 1 really pissed me off.

"Crying Wolf was easy. Hide under tank, equip sniper and thermal goggles and she can't hurt you. No-one can.
"

"I thought Metal Gear Solid 4 was pretty easy, I did die a bit but the only really hard part was Act 5. But just get the rail gun and kill the Gekkos.
"

"I did not find the end battle to difficult.

I hated the bit in the boat though, I literally just could not figure out how to get through, It probably took me over 10 goes, in the end I took all the high ground, and resorted to using the mk2 just incase."

"You can't use the rail gun when going for the BBE
"

"I got stuck on
3) Beginning of act 2 - hillside steps
and that's where my bbe run ended."

I really didnt like this game after the beginging of act 3....game got boring....but solid liquid fight at the end kicked ass.

I'm surprised with some of those.

1.  Motorcycle chase - Act 3
2. Vehicle chase - Act 2
3. Crying Wofl - Act 4
4. RAT PAT 01 escape - Act 1
5. RAY vs REX - Act 4

However, I'm only citing these because I have to, 2 to 5 are easy when put in comparison to number 1.

I think I bet Ocelot - final fight - in three tries, but all of them I got to the MGS3 part.

My frustration with that fight came from my Foxhound run, now that, took me ages to beat.

I ran through the game without ever using tranq. pistol / stun mines / solar gun (didn't have it) etc on regular soldiers (empty magazines ftw), only used that stuff on the FROGs. I used regular weapons on the beasts (mostly the Railgun) and the Shotgun (with stun) on the beauties. Finished the game in 4:06:07.

If I remember correctly, the three toughest parts where (in no particular order):

• Act 2 - Hillside steps
• Act 3 - Vehicle chase
• Act 5 - Ocelot (MGS3 version)

OP's list is actually pretty much the hardest parts of going for BBE, minus Crying Wolf. That was time consuming, but not hard.

"The only part I found difficult (more frustrating though) was the final fight with Liquid Ocelot at the end. It lasted too long and was boring as hell. The game is not a fighter and that section really proved it.
"