Apples are a perfect option. Also, you can try pears, broccoli and carrots, bread and ham.

I stuck my weiner in some fondue lastnight

In addition to many of the items listed above...Roasted mushrooms! Make sure you dry roast them so the cheese sauce will cling.

Wanted to suggest cornichons (small dill pickles) and cured meats, a la Raclette style, which may not be possible to source out of a specialty shop because even deli prosciutto is a little moist, as others have already mentioned small boiled potatoes.

We had the requisite bread cubes, plus roasted fingerling potatoes (cut in half lengthwise), roasted crimini mushrooms, chunks of seared rare hanger steak, endive spears, blanched tiny carrots, blanched broccoli and cauliflower florets, and blanched radish wedges.

There is a wonderful restaurant in NYC called Artisanal. They have fondue on the menu and offer a wide range of things to dip: Apples, fingerling potatoes, crudites, kielbasa, air-dried beef, chicken tenders & beef tips. That should get the creative juices flowing!

Apples and pears are great with fondue, and whatever bread you like - besides French or sourdough, I think a good light rye goes well with a classic Gruyere/Emmental type fondue.

Chunks/wedges of boiled or roasted potatoes work really well (if you can get tiny ones - red, fingerlings, whatever - you can use them whole.) I'm not crazy about raw broccoli/cauliflower, so I'd give it a quick blanch in salted water before serving.

Try cubes of walnut bread as well as the usual french bread. I think I'd like pears and apples more if the fondue has blue cheese in it.

#5. Pears
#4. Broccoli
#3. Golden Delicious Apples
#2. Crusty French Bread
And the #1 thing to dip into fondue: My finger! : D

I forgot about all kinds of veggies. I remember all of the Jolly Green Giant vegetables in cheese sauce I ate when I was a kid, and thought that they were "the greatest". For how many of us were they then only way we got our veggies? You can do it right with good fresh vegetables.

I don't think you can say what may be the "Top 5". That is so subjective. What do you like? Apples and pears can be great. Try different kinds of cubed bread. Make large croutons and garlic croutons for dipping. How about cubes of ham? Think of other things you like with cheese and go for it. I think that once you start, the possibilities will be, well, maybe not endless, but more than you would have thought.

Pears, broccoli and cauliflower, small carrots, cubes of ham, cherry tomatoes.

Bread and apples are good. I don't go further than that.