There are just so many...
Here a few:
1. The awesome cut-scenes & intro of Ninja Gaiden II on the NES
2. Encountering the 2nd level walker boss in Axelay for the 1st time. One of the coolest looking bosses I've seen in a shooter.
3. Playing Doom 1 continuously for 24 hours straight, back in 1994 on my good ol' 486 DX4 100MHZ.
4. Haggar’s grab & jump-slam move on the ground in Final Fight
5. Captain Commando's, Captain Sword, super move in CvsM.
6. Hulk's Gamma Crush move, where he smashes a huge meteor/bolder on the poor players head in CvsM.
7. Hulk's Gamma wave.
8. Iron Man's Proton Cannon in Marvel Super Heroes.
9. Entering the Alien Hive as a marine in AVP2 for the 1st time. Priceless!
10. Travelling / exploring through the huge alien world of Unreal 1.
11. Fighting against Buda Praevus Final Boss in Hexen II - Portal of Praevus Expansion. At some point, the fight grows so violent that the temple begins to crumble from the blasts emitted from you & the Boss. A shocking experience indeed!
12. The awesome Heavy Metal soundtrack of Lords of Thunder on the DUO.
13. The fiery wavy background in Thunder Force III Fire stage.
14. The final boss fight against Anubis in Zone of Enders 2. It resembled the fight between the Gods & Titans from Greek Mythology.
15. Encountering the 1st level Boss in R-Type II & watching the grotesque eye popping out from its stomach & firing a huge laser blast against your ship.
16. The awesome/epic soundtrack of Heretic & Hexen. Some of the best game music I’ve heard to this day!
17. The grotesque zombie, 4th level Boss in Gynoug / Wings of Wor, on the Genesis.
18. The Boss fights in Mega Man X3 & X6. The coolest of the series imo.
19. Batman’s level layout on the NES & some of the most memorable Bosses on any platform game.
20. The Guardian's Knight in TF5, firing a huge laser blast in agony for the last time, right before he blows up!
21. The Kick-Ass sound track & levels of AGONY on the AMIGA.
22. Fighting against the Alien Queen in Alien Breed SE '92 on the AMIGA.
23. Flying through hyper space in Gaiares & watching all those incredible raster effects on the Genesis. A truly awesome experience back in 1990!
24. Raiding the huge space citadel & encountering the Grim Ripper Boss in Gaiares.
25. Fighting gaisnt Z-Bandusy Queen in Gaiares with the Galaxy in the Background!
26. The intro of Thunder Force V (PSX) where a city gets annihilated by a nuclear laser blast by the Guardian’s Judgement Fleet. (Coolest & most sinister name I’ve heard for an armada of space battle cruisers)
And the quote:
In the first battle against the Guardian's weapons, created with Vasteel Technology, humanity suffered a crushing defeat
Priceless!
27. Hitler's face getting blown up at the end of Bionic Commando on the NES.
28. The ending of Strider on the Genesis, where Hiryu flies away on his kite. It then shows the earth while the sun rises from the side.
29. The fight against the 3rd level Boss in RayStorm, where flies into the scene over the water fall. The huge laser that uses against you, is just so cool!
30. Mega Man 2 on the NES.. The coolest levels & Bosses of the original series.
31. Ninja Warriors Again - Natsume at their best!
32. Fighting against a huge Air-Craft Carrier in 1945 Strikers II only to find out that it was actually a Mecha in disguise!
33. Fighting against Tidal Wave Boss, the huge air craft carrier in Transformers game on the PS-2.
34. The incredible "Warriors of the Wind" fantasy theme of Panzer Dragoon on the Saturn.
35. CastleVania - Symphony of The Night (PSX)... Best CastleVania to date, Nuff Said!