Everyone's answers seem to be ARAH, so I'll stay with that format. In no particular order:

'84 Ripcord- One of the first figure with loads of removable gear. Unlike Blowtorch, the color scheme on Ripcord was not yellows and oranges.

'97 Stalker- Best color scheme on this under-noticed mold.

'82/'83Cobra Officer- The Cobra figures from the first wave were much more detailed than the joes. More realistic web gear, folds in clothes, etc. This figure still holds up 25 years later.

Night Force Outback- They took a great figure and made it greater with dark colors.

Shrage- Like most of the OG characters, it took twenty years to become a figure. But it was worth the wait, even if it was just a new head on recycled parts.

Choosing 5 figures is tough, so I'll just choose 5 that come off the top of my head:

1. Snake-Eyes (v.2) - I was so bummed see Snake-Eyes in the 'Revenge of Cobra' mini-series and yet they didn't make a figure of his new outfit. I had to wait year before the '85 figs came out and it took a months before I saw one on the pegs. Needless to say, for a good 6 months, anywhere I went, he came along with me. Even now, if I see a cheap '85 Snake-Eyes, I'll snag him up on eBay. Just recently, I picked up a sweet black Aprilia motorcycle from Maisto that matches him perfectly.
2. Flint (v.1) - Same story as Snake-Eyes here. I watched the 'Revenge of Cobra' mini-series and couldn't wait to get this guy. I'll go with everything MikeT said. He's just about perfect, with the smirk and the accessories make him a winner. He's one of the most useful figs in my collection...he looks at home in the Sky-Hawk, the Dragonfly, AWE Striker, JUMP, anything else. Flint gets involved in just about any mission scenerio I can think of.
3. Lowlight (v.1) - As a kid, I didn't care much for him and thought is was kinda plain. Then one day in college, I posed him on my desk and for the next 3 years, he was perched on any random object in my room, ready to shoot at a moments noticed. There's a ton of detail on this guy...the knit cap, padding on his elbows, just the right amount of bulk, and the red goggles that set everything off just right.
4. Falcon (v.1) - Just a straight-forward looking figure. You look at him with all that gear and you know he's a Green Beret. The movie took him down a few points, but I just overlook that.
5. Ace (v.2) - I army-build this mold to no end. The later versions look more realistic with the olive green coloring, but sometimes it's nice to have a stray a little off the beaten path. The removeable helmet and mask are fine finishing touches.

I feel bad for leaving Dusty (v.1) off this list and that's why 5 is really impossible. Cobra's on the other hand, would be much easier

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Falcon V1 - Cool figure, good accessories - ultra military looking

Lifeline v4 (Battle Corps) - I have a soft spot for medics and this was the best medic mold around to me

Barbecue V3/ Payload V 3,4,5 - Great suit! I have used it as a pilot suit, hazardous environment, astronaut, diver etc etc.

25th Snake Eyes v 28 - the mold that saw allot of action in the Joe ranks so far as the anniversary line progresses.

25th Blue Shirt- currently my favorite cobra figure on versatility alone.

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I'll stick to RAH for these as well even though my collection is new sculpt RAH still is where I started.

In no particular order.

Repeater-- Loved the hip mounted gun.

Salvo-- The 5 shot missile launcher was too cool.

Buzzer-- The first figure I remember having. Made even cooler with Rock & Roll V2 arms.

Rock & Roll V2-- The gatling guns were cool and he looked like a true badass soldier from a movie.

Road Pig-- A real change to what was always released. A huge figure that totally dominated everybody when I got him. And he came with a cinder block hammer. And shoulder pads like he was one of The Road Warriors.

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I went with just my top 5 Gi Joe figures, as opposed to including Cobras. Here they are in no particular order.

Dusty v1-Still one of my favorites. Honestly I think the combo of face camo and the cloth sold it for me, but its such a great figure.

Falcon- Once I saw the movie, I had to own a Falcon. Still one of the best sculpted figures imo, just a great figure and character

Shipwreck v1-Not only did he come with cool accessories (which was a major selling point for me as a kid) He looked just like a friend of the family, who coincidentally served in the Navy as well. His character made me laugh on the toon, so the figure was always a must have.

Flash v1- My first ever figure. I was in awe of how cool it was to open the package and put his gear on. Ah the adventures we shared.

Snow Job-Again, the accessory factor, not to mention he came with the gun that would forever be associated with Gi Joe. Combine that with my love of snow, and he was yet another HAD to have.

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this is harder than I thought,...
sticking to RAH:

1) Alpine

I just loved his accessories. with the rope and hooks . plus all his exposure from the cartoon, made him one of my favorite figures

2) Storm Shadow V1

You weren't cool in school unless you had an Optimus Prime, and a Storm Shadow. Interesting that he was released the same year all those Ninja Movies started comming out, so recess was all about having a dude with Swords.

3) Snow Serpent V2

Not only did he come with an awesome snake boogie board, but a backpack that stored the board, and Fired Missiles!!!

4) Mercer V2

he just looked awesome to me

5) Snake-Eyes V3

The comic story with him getting this Costume from the Paine Brothers was the first Joe comic I bought,.. so this became my default Snake-Eyes..... (only topped by the recent 25th release)

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My list:

Flint (85): Basically, he was THE MAN in all my childhood playtime adventures. Just a great figure that I had lots of fun with

Beachhead (86): He was a close second to Flint. Everything about him was just so cool, though I never knew what to do with his 'purse'. And his giant head never bothered me in the slightest.

Recondo: The third member of my trifecta. These three were my unbeatable dream team. I like the figure a LOT, but I his appearance in the comic was also a major coolness factor.

Snow Serpent (85): Perfection in every way. Bad ass filecard, amazingly detailed sculpt, accessories coming out the butt... My all time favorite army builder.

Tie: Baroness/Storm Shadow: I probably used these two about equally, though in very different ways, and I love them both.

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Umm,

25th B.A.T. I really can't believe they nailed this one so well

NS Bombshell, cool figure, outstanding story, and a little bit of a build up waiting for her

Jinx, the OG chica badass, I gotta admit, she was my favorite female as a kid.

Battle Armor Cobra commander, though I see him as more of a trooper(especially after the 25a figure)

ANd I guess, the 25a red ninja, I don't like ninjas, I don't like that mold, but somehow he's just the fulfillment of something the line had needed for quite a long time.

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