Here you will find a number of chess variants for which I made a Jocly applet to play against.
This is a 5x5 miniature version of Japanese Chess (Shogi). It is not fully developed yet, and merely an exercise for how to handle variants with piece drops in Jocly.
An alternative design for drop variants, storing the captured pieces all around the board, rather than just on the sides.
Spartan Chess is an asymmetric variant, where the regular FIDE army (the 'Persians') have to take on a black army consisting of entirely different pieces (the 'Spartans'). That even pertains to the Pawns, which for the Spartans are 'Hoplits', capturing straight ahead, and moving diagonally. (And their initial double-push is a jump.) The strongest Spartan pieces are the Warlord (Bishop-Knight compound) and the General (Rook-King compound).
The Spartans have two Kings, and one of those is allowed to wander into check (and consequently can be captured). You will always have to have one King that is not under (pseudo-legal) attack, though. If one of the Kings is captured, Hoplits can also promote to King, to make the royal duo complete again.
A 10x10 variant that, in addition to all FIDE pieces, features several 'crowned' pieces, i.e. pieces that also move as a King. There is a Crowned Rook (Goblin), a Crowned Bishop (Elf), a non-Royal King (Dwarf), and finally a Wizard, which moves as a King twice per turn. This Wizard does not have to stop after a capture, and can thus perform double, hit-and-run and Rifle Capture.
To prevent early trading of Wizards, there are rules that restrict capture of Wizards: A Wizard cannot capture a protected Wizard (as if he was a King), while after capture of a Wizard the opponent Wizard is immune to capture ('iron') on the next move.
Werewolf Chess differs from orthodox Chess only in that the Queens are replaced by another super-piece, the Werewolf. This Werewolf moves and captures like a Queen, but only up to a distance of 3 squares. But it can jump directly to the second square in any direction, and thus move there even if the first square in that direction is occupied (by friend or foe). The piece jumped over can remain unaffected by this, but if it is a foe, it can also (optionally) be removed (i.e. checkers-like capture). This can even be done if the second square is also occupied by a foe, so that double-capture is possible.
The most exceptional property of the Werewolf, however, is that it is contageous. This means that a piece that captures a Werewolf instantly changes into one. (But it keeps its color, so it is like the Werewolf changes sides, and you effectively gain two of those against the piece). Kings are immune to this, and can thus capture a Werewolf without leaving you kingless. These rules make it very difficult (though not completely impossible) to trade both Werewolfs out of the game, and thus ensures that the game will almost never degenerate into orthodox Chess before late in the end-game. They also invalidate most of the common wisdom about tactical exchanges, such as that it is better to capture with the least-valuable piece first.
A variant on 8x8 that is all about diversity. It features many different fairy pieces, none of which would be able to force checkmate on a bare King. Almost every 'team' of two pieces does have mating potential, however. Because (next to King and Pawns) each player starts with 7 different pieces, and an 8th type can be obtained by promotion, 28 such teams consisting of two different pieces are possible. (In theory you could also get 8 homogeneous teams, but because most pieces are not likely promotion choices, these pairs would never occur in practice.)
Some of the pieces are 'bent sliders', the trajectory of which starts off in one direction, and then continues in another. Pawns cannot promote to the strongest piece (the Aanca, worth nearly 8 Pawns), and the next valuable choice (the Adjutant, worth about 7, not in the initial setup) is color bound, and thus might be useless to you if the promotion square is of the wrong shade. You could thus be forced to promote to the third-strongest piece.
A 10x10 chess variant that is remeniscent of the historic large shogi variants, and yet adheres strongly to the ancient chess traditions, such as 8-fold-symmetric pieces and oblique leaps. The initial army consists of 27 pieces of 18 types, densly filling the strength spectum from Pawn to Rook. All these pieces can promote upon reaching the 3-rank-deep promotion zone at the other end of the board, each to their own predetermined type, and some of these 18 promoted types are stronger than a Queen. Even the King can promote to a piece that is much harder to catch.
Many promoted pieces are divergent, meaning they have different moves for capture and non-capture (like the Pawn). Three of the promoted pieces have some non-chess-like capture moves, like in checkers, or rifle capture. There also is a piece that (both in promoted and unpromoted form) relays new moves to other friendly pieces in its reach. The promoted pieces, although stronger, in general are not fully upward compatible with the unpromoted versions, so that it will usually be a dilemma whether you should take the (always optional) promotion, or postpone it.
After having implemented a general method for handling piece drops in Jocly, and having made a great many number of 3d models of Shogi tiles, (which fortunately all have the same shape, so I only had to worry about the knji painted on them), I added several other Shogi variants. Not sure how strong the AI is, though; I concentrated on the game mechanics, and did not pay any attention to evaluation.
The dominant game in Japan, on 9x9 with dropping back of the captured pieces.
Similar in spirit to regular Shogi, but on 7x7, with a completely different set of pretty weird piece.
This game has been the dominant form of chess in Japan for many centuries, before piece drops were invented. It is played on a 12x12 board with 46 pieces per player. Which is rather large as chess variants go, yet the name means 'middle chess', as it was derived from an even larger game. Its iconic piece is the Lion, which can do two moves per turn, even if both are captures, and enjoys special protection against trading.
This 16x16 game with 78 pieces per player is basically an expanded Chu-Shogi version, which adds a 'zoo of weirness'. Amongst the added pieces are those that can jump an arbitrary number of others to capture (but over each other only according to some ranking rule), and Fire Demons, which do not only capture on their target square, but destroy all adjacent enemies as well. It required a lot of modifications in Jocly to implement this. I even spent some time on the AI, as I registered it for the yearly Tenjiku Shogi correspondence championship. I added some terms to the evaluation to encourage it to make the necessary moves in the opening for protecting its King from the jumping pieces, and prevent most early checkmates that way.