In the past I carried three plastic totes inside the bed of my Tacoma, but now carry two .50 caliber military ammunition cans. They're tall and slim, and I can now sleep in the bed of my truck on overnighters instead of having to remove everything but the Hi-Lift jack.
A buddy of mine, who bought another parcel of property adjacent to his and is cleaning it up, found the cans among the trash left behind by the previous owners and didn't want them. I found a use for them.
I used to carry a duffel bag inside my cab with personal supplies, but now carry a small tote and duffel bag. These are mostly filled with personal items for comfort in case I have to sit in my truck for long periods awaiting help in times of heat or cold.
All this stuff is inside my Tacoma 24/7 because in my daily travels I often see a trail I've been looking at and want to take and on a whim take it. Never know what trouble I might find myself into ...
And because of living in rural Nevada, if I break down on some back road or even I-80, it might come in handy.
For more details on what I carry in my containors, go to:
http://www.gbr.4wdtrips.net/4x4/toytaco.html#storage... and ...
http://www.gbr.4wdtrips.net/4x4/tacoma-carryon.html