So, I’ve written variant rules for all of these:

Sharks and Ladders
Also known as Drakes and Ladders, Snakes are replaced with Sharks. Landing on a Shark results in losing the game immediately. Games tend to be short and have no winners.
Snakes and Adders
Replace all Ladders with Adders. Adders work exactly like Snakes.
Gates and Ladders
Ladders connect each section of the board. Sections are bounded by two impassable gates which reverse your direction when reached.
Snakes and Llamas
Replace Ladders with Llamas. Landing on a Llama allows you to pick it up, and cancel out the next snake you land on.
Snakes and Lazers
This is a roborally variant, where the snakes have lasers that fire each turn. Avoid.
Snakes and Lagers
Also known as Snakes and Bladders. Remove all Ladders. Landing on a Snake gives the player a choice between using the snake, or having a drink. The player loses if they need to take a bathroom break.
Snails and Ladders
Replace all Snakes with Snails. Snails reduce the value of all your future dice rolls by 1, (minimum 1)
Stakes and Ladders
A betting variant. Replace all Snake spaces with Stake spaces. When a player lands on a Stake space, they either choose to double the value of the game’s stakes, or forefeit (much like doubling in backgammon)
Cakes and Ladders
Replace Snakes with Cakes. If you land on a cake space, you may eat the cake. You may not take turns until you have finished the cake.