One of the cheat codes gives you 9,999 ammo for every weapon. Normally the amount of ammo you can carry is capped much lower than that, but obviously the game can handle more.
Has anybody ever done a mod that can let you collect up to 9,999 ammo for all the weapons without using the cheat codes? You get the normal amounts when you pick something up, but I've started the game on Monday, grabbed a pistol and a can of gas, and gone to Tora Bora with just those two weapons and wound up with full ammo for the machine gun before leaving the sewer and a bunch of machine guns lying on the floor.

That, and I recall the Marathon Trilogy had an interesting feature, that made the so-called highest difficulty level called "Total Carnage" easier than the second-highest "Major Damage" because playing on TC uncapped the amount of ammo you could collect, making the parts where you have to deal with ammo starvation and lots of enemies much easier to deal with. Stock up on the easy levels, and you have plenty of ammo for the harder levels. I found it more fun. I'm looking for a mod to replicate Marathon's feature.