I’m a big proponent of mini-games to keep your dungeon-crawler interesting. You can use these as activities in town (carousing, gambling, racing, wrestling, brawling, etc.) or use them for challenges in an adventure (traps, negotiations, digging out a passage, crossing a river, etc.).

Tic-Tac-Toe Opposed

Traditional tic-tac-toe, but claiming a space requires a skill check, perhaps one that’s predetermined by the space.

Good for a negotiation, battle of wits, or battle of skill.

Tic-Tac-Toe Solo

Traditional tic-tac-toe, but claiming a space requires a skill check (which you can make predetermined or player-selected). The opposing plays are just randomly selected and don’t need to succeed at a skill check.

Good for escaping a collapsing dungeon or otherwise trying to accomplish something where avenues to success may be randomly closed off.

Skill Challenge

Make 4 relevant skill checks before getting 3 failures.

Good for crossing a dangerous river, brewing a potion, etc, where failure is a real possibility.

Progress Checks

Make 3 or 4 relevant skill checks, each one of which represents some progress. Failure just means you don’t make progress (but may cost time, hp, gp, etc.); only natural 1 is an actual failure.

Good for relatively safe and easy challenges, like crossing a small river, walking a tight-rope or narrow ledge, or sneaking across a courtyard.

Attrition Rolls

Each action does 1d6 “damage” to a task with 20 “hp”. Each roll costs something (time, noise, gp, hp, etc.)

Good for safe and easy challenges, like digging out a passage, breaking down a door, building something, etc.

Hail Mary Rolls

Each hero has a few chances to accomplish something but only succeeds on a natural 20. There’s no penalty for failure beyond the loss of the chance. Two tries per round; a skill or ability bonus might apply.

Good for stopping a trap mechanism with a thrown rock (use DEX) and other situations where time and/or opportunity is short.

21 Opposed

Roll d6s to get close to 21 without going over. Each roll may have a cost (time, noise, gp, hp, etc.). Higher total under 22 wins.

Good for gambling, duels (where going bust means opening yourself up as you press your advantage), opposed attempts to woo or influence (in which the party being wooed can get fed up), and other situations where the further you go the better, as long as you don’t go too far.

21 Solo

Roll d6s to get exactly 21. Each roll has a cost (time, gp, hp, etc.). If you go over, you fail the challenge or have to start over. You can add up to your proficiency bonus (for a proficiency bonus of 2, you can add 0, 1, or 2).

Good for attempts to woo or influence (in which the party being wooed can get fed up) and other situations where the further you go the better as long as you don’t go too far.

Race Rolls

All participants roll 2d6 as fast as they can to get a 12. First to get two 12s wins. Add an “obstacle” skill check here and there, if appropriate (race thru a crowd rather than on clear track).

Good for races and simple chases.

Chase Rolls

You have a head start determined by the GM. Roll two d20s. Choose which will represent the route you’ll take and make a relevant skill check against that difficulty. The opponent has to make checks against the same difficulty. If you fail and the opponent doesn’t, the opponent gets closer to catching up. If the opponent fails and you don’t, you get further ahead. If your head start is reduced to 0, the opponent catches you. If you stretch your lead enough, as determined by the GM, the opponent loses you or gives up.

Good for chases and complex races (where you have no head start and, instead of catching you, the opponent passes you). As a foot chase, the route can be thru clearer or more difficult ground, over obstacles, etc. As a sailing ship or aerial chase, the route can involve executing difficult maneuvers.

Push Your Luck

With each 1d20 roll, gain 1d6 (gp, luck, etc.). On a natural 1, you lose all gains.

Good for carousing and other situations where more is more… unless you go bust.

Double Your Money

Risk something (usually coins) to gain double (if you bet 5, you either lose 5 or win 10). Check difficulty 14 to win. On natural 20, roll again to win the same amount again without risking anything further.

Good for gambling.