I don't recall ever having seen a GW sculpt of a guardsman with a storm bolter.
Are you sure that this wasnt just an option for a model, and your friend converted the model, as opposed to a GW model that was made obsolete?
TL;DR: Pics or it didn't happen.
Add some more as I remembered:
CSM Bikes with Sonic Blasters.
CSM Preds with Sonic Blasters as sponson weapons.
CSM Thrall Wizards.
DE Archon on Jetbike.
GW produced a CSM Lord/Sorcerer with a Kai gun (daemon weapon) and lightning claw. No more Kai guns and it's too big to pass as a combi-bolter so another invalidated model.
Seems most of the examples came out of when the CSM codex lost a lot of it's flavour.
scout sgt namann from the dark angels...gw made a model.... he doesnt exist any more
capt sicarus with lightning claws.. special edition model now that option doesnt exist
eldar bonesinger model special edition.... never existed in any book i ever saw.. made a good spirit seer if you converted it
familiars and servo skulls....
older armies
sgt centurious LOD.. doesnt exist anywhere
All the above can still be used.
Namann? Scout Sarge.
Sicarius? Captain with lightning claws.
So on, and so forth. Servo skulls? Warriors in a retinue unit thingy.
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Some catachan models had them. Here is a link to one I could find [url]http://www.ebay.co.uk/itm/GW-Warhammer-40K-Guard-Catachan-Captain-with-Power-Fist-/400333957281?pt=UK_Toys_Wargames_RL&hash=item5d35c 368a1[/url]
How about these guys.
[url]http://store.wargamingtrader.com/system/files/imagecache/product_full/E887%20-%20Eldar%20Guardians%20with%20Lasguns%20x%203%20%2 01990%20%20%20%20%2011-10-30.jpg[/url]
When 4th Edition hit these guys were gone and many of us old time Eldar players have quite a few due to the way we had to make our Eldar army.