In Gear 2, 3 and 4, Luffy has several of his original attacks improved according to his respective gear forces.
Gomu Gomu no Pistol is Jet Pistol in Gear 2nd, Elephant Pistol in Gear 3rd and Culverin in Gear 4th.
Same goes for Bazooka, and without Gear 4, it stands for Gattling Gun as well.
These just mere examples, as he has quite a lot of attacks. I wouldn't even ask about all of them, so I'd like to focus on one absence I noticed.
Luffy has Gomu Gomu no Yari which appeared as Rhino Schneider in Gear 4. Does it have Gear 2 (and 3) versions?