First off, Hello! I've been browsing these forums for the last month and I decided to register to put in my 2 cents. This might be somewhat lengthy, hope you don't mind.
I don't think anyone has yet mentioned being able to use the butt of the sniper as a melee weapon (It was the butt of the sniper, right?) That would make a nice alternative to slappers, maybe do twice the slapper damage.
I'd really, really like to see a nighttime version of cradle with some dim lighting scattered about the towers and 2 buildings in the center. That would be amazing.
I was thinking maybe a combination of Facility frontzone, backzone AND the runway map. Hear me out, you could have objectives like the M16 team has to get from the facility to the plane on runway and escape while completing objectives and the Janus team has to prevent it. Eh?
On the topic of game modes, maybe Capture the briefcase or king of the hill, they WERE from Perfect dark but the 2 games had a similar gameplay style and I think those modes would fit great in GE:S.
Bunker, need bunker. And if the Siberia level too, that's a must. Maybe even another objective oriented map combining Siberia and bunker? Something to bring back the nostalgic mission feel from the original.
Dual wielding sounds nice but it would have to be tricky to get 2 weapons, that or their damage would have to decrease a bit so that you aren't raping everyone with dual phantoms or RCP90s.
The golden Gun needs to show up less in random weaponsets.
More clothes colors for the other characters perhaps? Why does only bind get 'em? =P
I agree with a point stated earlier about the gun firing should cause light to appear from the muzzle flash in dark rooms, it would help you to see who you're shooting at in the dark and add a great effect.
Oh and some larger maps for Team deathmatch, I love that game mode. The whole M16 vs Janus thing is a lot of fun, but no one is ever playing on a TDM server or hosting one. =/
Oh! I almost forgot! More Achievements! These have been so fun, unfortunately I'm reaching the 00Agent mark on a few of them and I feel I got there way too quickly. They need to have higher requirements and I believe the License to kill achievement should have the A, SA and 00A difficulties too but it should go something like: A = 1,000 Kills, SA = 5000, 00Agent = 10,000. It sounds like a lot but if you play as often as I do it would seem perfect. =P
Besides it SHOULD take a lot of time.
Now for a few things I've just wanted to say...
The Aiming is perfect, I don't see why so many people complain about it, it just takes practice. I've gotten quite good after learning on Beta 1.1h. It really doesn't take long at all to learn how to get 70% headshots. You just need to learn how the weapons act and where the center of the screen is. Adding a crosshair or any way to enable one is a horrible idea, people need to just learn how to play and practice, that's all it takes. My all time favorite aspect of GE:S is the different style of gameplay. I'd hate for it to turn into a game like all the rest.
One thing that's been bothering me is people calling me a n00b on MWGG for using the Golden Gun... this irritates me to no end and a lot of people just leave servers because they die too often and don't even TRY. Is there a way to make it more noticeable that it's not a regular deathmatch game mode? I think people enter those servers oblivious to the gameplay type.
That's all I can think of for the time being. =]
EDIT: I forgot to ask, is it possible to make it so when a door (like the metal ones in facility) is closing you can reopening it while its closing so you don't have to wait for it to close before you open it again? Sometimes this is a must to escape a fight or even being able to close the door behind you to block off the enemy for just a little longer so you can grab the gun in the locker room and kill him before he manages to get inside. This was in the original game and I definitely used the technique to save my ass a few times.