Arisaka rifles and carbines:
Type 38 -- 6.5 mm, standard infantry rifle beginning in 1905.
Type 38 carbine -- Shortened type 38 rifle. A variant, for paratrooper use, was made with a hinged stock through the wrist. Not very successful.
Type 44 carbine -- Introduced in 1911, permanent folding bayonet.
Type 97 rifle -- Sniping version, with telescopic sight and turned-down bolt handle.
Type 99 rifle -- Chambered in 7.7 Arisaka and adopted in 1939.
Type 99 carbine -- Shortened version of the rifle.
Type 2 -- 7.7mm, interrupted screw breech take down, supposedly for paratrooper use.
Handguns:
Type 26 revolver -- Double-action only, break top, chambered for a proprietary 9mm round very similar in size and power to the .38 S&W round.
Type 04 Nambu -- Original semi-auto design in 8mm Nambu, adopted in 1904. Grip safety, no magazine safety, adjustable rear tangent sight.
Type 14 Nambu -- Modification of the 04, adopted in 1925, no grip safety, has a magazine safety, fixed rear sight.
Type 14 Nambu, "Manchurian" modification -- A Type 14 with an enlarged trigger guard to allow use with a gloved hand.
"Baby Nambu" -- Very rare, in 7mm Nambu, apparently originally designed for commercial sale, with most known going to high-ranking officers. Very very expensive when encountered.
Type 94 Nambu -- Horrific gun, intended originally for commercial sale, introduced in 1934, virtually nothing to recommend it.
Submachine guns:
Type 100/40 and Type 100/44. Both variants on basic theme. Blowback operated, box magazine, blowback operated. Some 100/40s were made for paratroopers with a folding stock hinged through the wrist. Not many of either type issued.
Machine guns:
Japanese had a lot of experience with machine guns, again not much to recommend them from a mechanical point of view. With one exception, Japanese machine guns required the use of either oiled cartridges or an oiling mechanism in the gun to ensure that the action didn't rip the head off the cartridge during extraction. Not a good situation in a dirty combat zone. Many light machine guns also had provisions for attachment of a baoyonet. Charge.
Type 3 (Model of 1914)/Type 92 heavy MG -- Both liberal copies of the French Hotchkiss gun. The Type 3 was chambered in 6.5mm Arisaka, the Type 92 in 7.7mm Arisaka.
Type 11 -- Introduced in 1922, squad-level gun. Fed from 5-round Mauser stripper clips that were dropped into a hopper. Theoretically a good idea, as you can get ammo from riflemen if you run out, but rifle ammo proved to be too powerful. Instead of redesigning the gun to work with the standard rifle ammo, the entire concept was defeated by adopting a less powerful round.
The Type 92 had a slightly different gas system and different kind of grips. Other than that, very similar guns. Both fed from 30-round stamped steel strips.
Type 96 -- 6.5mm, designed to replace the Type 11, but never did. Based liberally on the Czech ZB, and looks similar to that gun or the British Bren, but with few of the benefits those guns enjoyed. Hopper mechanism replaced with a 30-round box magazine. Many had provisions for mounting the same type of telescopic sight found on the Type 97 sniping rifle.
Type 99 -- Essentially a Type 96 updated to 7.7mm, but at long last provisions were made for primary extraction of the fired cartridge, meaning that rounds no longer had to be oiled before use. Altogether the most successful and reliable of all Japan's machine guns.
Anti-tank rifles:
Type 97 -- A conglomeration of ideas from European guns. Chambered in 20mm. Complex operating system using a combination of gas and blowback, with the action allowed to recoil along a slide against heavy recoil springs an an oil buffer recoil system. Fired only fully automatic, but at a low rate.