Reason? My character models and animations were fubared beyond belief.
-Start a new game...look DOWN when you get control of the camera, and realize you are like 3 to 5 feet ABOVE the Doc's head level.
-Go to sit on the doc's couch to answer his questions...hit outside camera view and realize you are sitting half a foot UP, and 4 feet FORWARD of the couch.
-Weapons and body parts randomly intrude on first person camera while running around.
-Weapons, especially in stealth, bounce around the screen erratically and sometimes vanish. Iron sights mode USUALLY brings them back into view, but the process starts over again!
Cut to running the game with all mods unchecked: Everything working *NORMALLY* except the bouncing weapons ( I hear this is a F:NV issue, not a mod issue perhaps?)
Just assume that any mod that MIGHT have caused this...I probably had installed...and name them off and why you think they cause it, and I'll contact the author's and see if I can help them stomp some bugs

Here is my load list
(click on spoiler)
Spoiler
FalloutNV.esm
MercenaryPack.esm
Ambient Temperature.esm
CFWNV.esm
Inventory Access.esm
IWS-Core.esm
More Perks.esm
Weapon Mod Expansion.esm
FOOK - New Vegas.ESM
TravelingMerchantFix.esp
DarNifiedUINV.esp
HUD Extended.esp
HUD Extended - Ambient Temperature.esp
NewVegasBounties.esp
UHNV.esp
markers.esp
FOOK - New Vegas.esp
XFO - 5da - Skills - Sneak - mild.esp
XFO - 6e - Pacing - Vanilla (JUST No Cap).esp
XFO - 8b - Speed Increases.esp
XFO - 8c - Karma Rebalance.esp
XFO - 8d - Gore Changes.esp
More Perks Update.esp
xatmosSkillPerks.esp
Better Tag Skills.esp
DK_BulletTime_NV.esp
WMR_WME_S.esp
QS_Blackwolf_NV_Backpackmod.esp
Eyepatch.esp
Powered Power Armor.esp
Ambient Temperature - PPA.esp
Realistic_Repair_NV.esp
Light Step ED-E.esp
UnlimitedCompanions.esp
aaaJNFSniperZooming.esp
noautoaim.esp
FONV - Real Time Lockpicking and Hacking.esp
Jump Fall Fixer.esp
Fellout.esp
ColdTurkey.esp
UsableCigarettes neunen Ver for New Vegas.esp
PotG_Cowpoke_Pack.esp
Bashed Patch, 0.esp
Total active plugins: 43
Total plugins: 54
MercenaryPack.esm
Ambient Temperature.esm
CFWNV.esm
Inventory Access.esm
IWS-Core.esm
More Perks.esm
Weapon Mod Expansion.esm
FOOK - New Vegas.ESM
TravelingMerchantFix.esp
DarNifiedUINV.esp
HUD Extended.esp
HUD Extended - Ambient Temperature.esp
NewVegasBounties.esp
UHNV.esp
markers.esp
FOOK - New Vegas.esp
XFO - 5da - Skills - Sneak - mild.esp
XFO - 6e - Pacing - Vanilla (JUST No Cap).esp
XFO - 8b - Speed Increases.esp
XFO - 8c - Karma Rebalance.esp
XFO - 8d - Gore Changes.esp
More Perks Update.esp
xatmosSkillPerks.esp
Better Tag Skills.esp
DK_BulletTime_NV.esp
WMR_WME_S.esp
QS_Blackwolf_NV_Backpackmod.esp
Eyepatch.esp
Powered Power Armor.esp
Ambient Temperature - PPA.esp
Realistic_Repair_NV.esp
Light Step ED-E.esp
UnlimitedCompanions.esp
aaaJNFSniperZooming.esp
noautoaim.esp
FONV - Real Time Lockpicking and Hacking.esp
Jump Fall Fixer.esp
Fellout.esp
ColdTurkey.esp
UsableCigarettes neunen Ver for New Vegas.esp
PotG_Cowpoke_Pack.esp
Bashed Patch, 0.esp
Total active plugins: 43
Total plugins: 54