DA Wallet: I still have my DA leather wallet (circa 2007), but lost the pen (well... it finally self-destructed..) and haven't resupplied the little paper-pads. But... I have DollarTree notepads in my jacket pocket, and a pen, so I'm covered.
GTD plastic folders, that I take back and forth between Home and Work. I use traditional workflow to process papers (I'm a clinical social worker): Labled - IN; CPRS (paperwork capturing that now has to be processed into a EHR; Scan; After Scan (when I'm reviewing my scans in Outlook); File; Shred; Read/Review; Home (to remind me to unload stuff needed at home. Works really well, and I can do batches of stuff (Scan; After Scan; Daily Shred).
Pocket recorder: This dynamite $50 investment is the best capture tool. After seeing a client, I spend a couple minutes reviewing the paper notes and capture top-of-mind thoughts. When on the road, I also use it for things that pop in my head. I could be doing the actual processing a couple days later, and the audio recording has capture everything I had observed and assessed. A lot of it is subtle observations that are difficult to write down in the moment.
iPhone: Synched to OneNote which is my trusted GTD Project and Action tool. I've been seeing some posts lately on OneNote and Excel. I'm using a Notebook (GTD); Sections are the contexts (In, Checklists, Phone, Computer, Office, Home, Agendas, Read or Review, Wait-For, Errands, various Project sections; Pages are then the "Actions within each section. By using this method, I can move an action from one section to another, for example: I've done a call and then can prepend with the date (12/26) and drag over to Waiting-For. I typically have to drag it up to the top, so that the newest date on top, but that's no big deal.
Having the iPhone in the field is great for review client Project and Action Support. Also, when in foodbank line, and have a couple minutes, I can discreetly move away and check my PHONE list for some calls to do during "weird time" - those unschedule moments that become available.
Excel is more used on laptop at the office. That's vital for keeping track of recurring actions (annual; 6 month; 3 month; current). It's basically an electronic tickler file, but it keeps me completely focused in the moment and for the week, and little slips by. If it does, then I change the color of a field, and address first thing in week. Each client has their own row.