As far as adventurous ideas go for 21 year olds...
Some of the most fun times I've had in answer to the "uh, what do you want to do now?" question have involved just walking around and seeing where it takes you. Wandering through Home Depot one evening with the other two members of the "Jessica trinity" (all 3 of us happened to be of similar size, martial arts skill, and name and enrolled at the same kickboxing school so we quickly became the trinity), we decided to buy some planks to practice board breaks. Then we decided to buy a few things to fix Jessica's chair, and then we decided to see if we could make a new table... and it went from there. Chair fixed, very cool if not completely stable end table, and two empty bottles of wine made for a good evening.
Or you can try "advanced people watching." People watching is fun enough, but with the 2 of you, try coming up with your take on each person's life based on a few seconds of observation. You'll never know if you're right but it's incredible fun. Some are even worth writing down and using as the basis of short stories.
When was the last time you checked out a toy store? There are indeed games for people of all ages in there.
Those are a few...
Calli