Mine would definitely be completing Ravenholm in The orange box with nothing but the Gravity Gun.

All Gold medals in PGR 3 and the Sniper Achievement in Battlefield 2 where you had to kill 4 people with one clip.

Agreed on the "Zombie Chopper" achievement, also the "Mile High Club" achievement in Call Of Duty 4 pretty much made me go insane.

at the moment killing frenzy on halo.

"Agreed on the "Zombie Chopper" achievement, also the "Mile High Club" achievement in Call Of Duty 4 pretty much made me go insane.

"Mile high club was the most frustrating achievement I've ever experienced

Carrying that damned Gnome for 3 hours in Orange Box. But hey, 99/99!

All of my Burnout Paradise achievements...I love this game.

Whatever it is for beating GeOW on Insane, I think its commando. Beating RAAM was insane, I think it only happened by default of trying so many times.

probably Mile High Club

"Zombi said:

"Agreed on the "Zombie Chopper" achievement, also the "Mile High Club" achievement in Call Of Duty 4 pretty much made me go insane.

"Mile high club was the most frustrating achievement I've ever experienced

"

The "Liberty City Minute" achievement in GTA IV. Nothing really special in and of itself, but I got it on my first play through.

Definitely has to be beating guitar hero 2 on hard.  Even though I've 5 stared everysong on hard, Beat jordan on expert, and beat guitar hero 3 on expert since then, beating gh 2 on hard was something I thought I would never do. But I proved my pinky finger wrong!

Mile High Club I am quite proud of, and today I got the "Let Sleeping Rockstars Lie" or something in GTA4, and it was like kill a developer! Thought that was pretty cool.

"Mile High Club I am quite proud of, and today I got the "Let Sleeping Rockstars Lie" or something in GTA4, and it was like kill a developer! Thought that was pretty cool."

mile high club to name one, but i have more

Definitely exploring the entire island in Test Drive Unlimited. Took me forever and wasn't too stressful. All I did was listen to music, drive around, and enjoy the scenery. It was really nice to finally get it done.

Mile High Club in CoD4.

The "Kick the Bucket" achievement on Guitar Hero II was pretty momentous.

Halo 3 on Legendary means a lot to me.  It isn't a difficult achievement, but it represents six long years of salivating over Halo plot speculation and mired endings. 

The ridiculous Dead Rising achievement for killing Willamette's population in undead was amazing, also. 

More to come, hopefully?

The 50 Million Drift on Juiced 2

"Mine would definitely be completing Ravenholm in The orange box with nothing but the Gravity Gun.

So scary, so awesome.

"

I have 78/99 achievements for the Orange Box. Most of the ones I'm missing are from TF2.

The ridiculous Dead Rising achievement for killing Willamette's population in undead was amazing, also. 

All the Halo ones. 1000/1000

and 400 smashes in Burnout Paradise :D

surive 1.000.000 in geometry wars. And complete all 50 levels in N+. I also think the Mile High CLub and kill 4 in a row in halo3 were good and challenging, but nothing compared to the first two.

I don't know why but when I made half a million in GTA4 i felt really rich.

1000/1000 for Halo, Mile High Club for COD4, and beating Mass Effect on insane. Soon, I'll have 1050/1050 for Mass Effect =D

Probably 100% a song on Expert on the Drums For Rock Band...

But i'd have to see a list of them to decide...

The most recent achievement I have is getting a 90% relationship with all my friends on GTA4.

Mine would be the EA Moderator achievement in ProStreet. Took me so much trouble to get that achievement.

Mines is Seriously.... from Gears of War. Sure, it's not all that hard, but it takes a lot of playing time to get it, I was surprised I managed to play that long. :)

I have to say "Zombie Genocider" for Dead Rising...there's 4 hours of non-stop carnage...

"Halo 3 on Legendary means a lot to me."

getting the kill 53 thousand zombie achievement in dead rising...

Probably the achievement for getting an S rank on bloody palace mode in Devil May Cry 4 :)

Completing GTA4 in under 30 hours or something. Mostly because it came as such a surprise that I'd be accredited for doing so.

Yeesh... I was really pleased with finishing Ninja Gaiden 2 on warrior difficulty, though I am no match for that game on mentor XD

Either that or my full 1000/1000 for Oblivion. I think a lot of people have that, but it was still a great feeling when I got that last few points.

Finally finishing Oblivion late last year, despite finding it a dreadfully boring RPG. It's quite an achievement to play through a game you really don't like...

I would have to say... The 1000 note streak on Guitar hero 3 or Kick the bucket on gh2

Beating DOOM on UltraViolence (Rampage achievement)

Took a few days, but i was proud

Ravenholm in The orange box with nothing but the Gravity Gun, Seriously-Achieve 10,000 kills in ranked online matches GeOW

the simpsons press start achievement , best achievement Evaaaaaar

My precious Mile High Club, and my die 1000 times in N+ achievements :)

Getting my Elite in the first Rainbow Six Vegas, but the master of ceremonies was super hard.

Mine would probably be getting 1000/1000 for COD4. I tend to like rubbing that fact in my one friend's face.

I would have to say the "Developers Curse" achievement on KUF:Circle of Doom. That took freaking FOREVER.

Mine is the purple heart achievement in call of duty 3. Oh wait you said proud  : (

AN-I-MAL!!! achievement on Rock Band for beating expert drums. It's the only achievement I've really, really strived to get.

For me its got to be either the Mile High Club achievement in CoD4 or Seriously in GeoW.

i would be proud of COD 4 on Veteran achievement, but at around the last level, after I HAD JUST GOTTEN PAST A CHECKPOINT THAT I MADE ME STOP PLAYING THE GAME'S DISC IS UNREADABLE!!!! FUCKING BROKE XBOX!!!

None really, I still need to play more games before I decide on that