Careful, paranoid Puma will say we're the same person again, or that youre just upping your post count....
To
OP: one weapon* which IS different depending on what you are trying to deal damage to are lightning claws and their variants. These specify a reroll "to wound", and therefore *don't* work on vehicles - as you dont wound vehicles, you roll to penetrate armour.
*and Kharn, as apparently pulling skimmers out the air on a 2+ was a bit too good