Wow, hard to choose just 5. Here goes (in no particular order)

1. v1 Iron Grenader

2. 2001 "laser" Viper

3. v1 Night Viper

4. v1 Shock Viper

5. v1 and v2 Headhunter.

In no particular order,

Alley Viper, the blue one from 2002;

Blueshirts;

Neo - Vipers blue version;

Eels v1;

SAW Vipers v1.

No particular order:

Iron Grenadiers (v1, although I do like the new-sculpt ones as well)
Red Ninja (TRU 6-pack)
BATs (Internet-exclusive 6-pack)
Alley Viper v2 (yellow & black)
VvV Viper (v2, in the classic blue & red)

Wow, that was difficult. Ask me again another day and I might say something else instead of that VvV Viper...!

for me

viper v1
B.A.T 6 pack
neo viper
T.A.R.G.A.T
night viper

25th Ann. Cobra Troopers
25th Ann. Cobra Officers
VvV wave 7 Vipers
Viper Pit Vipers
DTC Snow Serpents

These are my favorites right now. I love the original stuff too like V1 Troopers, Officers, Vipers, CG's, etc. but they are way too expensive to army build like you can do with the newer stuff.

Anything crimson
Anything IG
Any original sculpt Vipers
Cobra Officers/Soldiers (Original)
Steel Brigade (All versions)

D :D

My faves:

1) Crimson Guardsman: they just look cool! Especially the new sculpts witht he removable helmets!

2) Iron Grenaders, V.1: another cool figure

3) Green Shirts: at last some joe "Bullet Stoppers"!

4) Alley Vipers (both Versions): Acide from the silly colors, the shields and guns looked cool.

5) Bats (the ones based off Sigma Six) are the coolest, and witht he six pack, you could make an army with a few packs.

1 - Motor Vipers

2 - Alley Vipers

3 - Night Vpers

4 - BATS

5 - Viper ('86 & Pit)

Here's mine with no particular order too:
*Crimson guards (operation crimson sabotage)
*Cobra infantry forces 2004 6 pack
*Cobra night watch 6 pack
*Cobra vipers (viper pit version)
*Alley vipers (2002 blue and black version)

This is very hard sice it changes all the time for me. Right now its Range vipers but my top 5 favorite are

#1 Crimson Guard(85) (need more)
#2 Range Vipers(90)
#3 Vipers(86) (I'm all set with them)
#4 Eels(85) (wouldn't mind getting a few more)
#5 Alley Vipers(89) (just a couple more and i'd be set)

Cobra Freak :D