I like to do a lunch of honey on bagels.
Also, if you're looing at tuna there's a couple other similar bagged fish. They're all good on crackers.
Can also get a supper small thing of mayo and a bag of chicken and have that on a bagel. Get the onion bagels and it adds a little extra flavor.
The majority of my travel lunches have something to do with a bagel because they can actually fill you and the cram good in the small pack I keep all the day use stuff in.