With the group of people I play with, we are using a pfs like campaign set up to allow players to jump in and it of games with some simple rewards systems for simplicity. Players get flat exp and money based on the cr of the encounter and item buys at discounted prices at the end of the campaign. Everyone is first or second level and I am struggling to make challenging encounters with only a cr1 limit. I had one session where most encounters were cr2 and the players were over leveled by the end of the session.
Basically, what are some challenging low cr encounters you can make? What are some inventive traps? pit falls are a cr1and still relatively easy to spot out. I've triedKobold crossbowmen in tight corridors with alchemists fire already.
A climbing animal in the forest. Especially if they have to catch it rather than kill it. Maybe a raccoon or monkey that steals some gear then runs away.
Look at thw environment rules carefully. Even a couple of small monsters can be a problem in their native terrain.
An NPC with a trained animal or two. Ranger, Druid, or just a grouchy guy with two pitbulls. Or a warrior on a horse.
A hostage situation -- someone is locked up in a house and the Pcs have to break in or sneak in.
A battlefield where Acrobatics checks are called for to move around.
Maybe PCs need to get on board a ship anchored out inthe river (swim, boat), with a watchman aboard (level 1 rogue with a trained monkey), too much noise will alert a couple more sailors (rogues with acrobatic skills, or warriors) and finally they have to deal with the captain (a level 2 cleric of -Abadar or someone).