If you're looking outside the scope of games, a Classic II is far better for productivity programs, especially newer ones like Word 5.1 (which runs on an SE but runs much better on a Classic II). Some games do run smoother (Battle Chess is the one that comes to mind for me) but I think you'll notice the most improvement in productivity software.
Try playing some sound files on it. Convert something recent to the System 7 format, then play it. I remember doing this with an SE/30 once, so a Classic II can handle it just fine.
You can test the limits of your Classic II by installing 7.6 on it (the SE can only go up to 7.5.5). Alternately, find 6.0.8L and watch it scream. Personally, I like mine as a 7.5 box since it's a fast enough Mac to handle it (mine has 10MB RAM, which you'll need if you want to max out the System).
If you want an add-on, track down a FastMath Classic II math coprocessor. They're rare, but worth every penny if you want to use it for something which requires them. Again, you'd be doing it more for proof of concept these days, but it would give you something to play with on this machine.
EDIT: Just saw the above comment about the mic port. Find a microphone and give it a try