1. Find (or Build!) Narrow Shelves
By finding a purpose for the gap, you're making it look purposeful. Measure your gap, then head out and scour stores for a narrow shelf unit that fits perfectly with your cabinets. Many spice racks fit the bill, like this one from The Container Store. But if you can't find the right fit, consider commissioning someone to build a shelf unit to your specifications, it could be cheaper than you think.
2. Install Hooks to Hang Pots
We've never met a kitchen that couldn't use an extra place to stash pots. Anchor in a few heavy-duty hooks from the exposed side of your kitchen cabinets and use them to hang pots and pans when not in use.
3. Buy a New (Wider) Appliance
If the gap is killing you and any attempt to make use of it makes your tiny kitchen look cluttered, splurge a little on a luxuriously wide oven or fridge. After all, it seems like your kitchen was built to have one. If you're rocking a 30-inch oven, upgrade to a commercial-grade 36-inch model, like this one. You'll get to close the gap, plus add in extras like 2 bonus burners and plenty of pan storage.