That's a hard question since my favorite Bond film doesn't really have any gadgets (the safe cracker wasn't that cool enough to be considered a gadget).
I kinda like the rocket firing cigarettes in You Only Live Twice. You could really have fun with a couple packs of those.
Well, if we're going to set rules that say "PROP ONLY", I'd want the original prop of the Golden Gun... followed very closely by OddJob's Hat.
If we say Bond device only, I'd love a gyrojet pistol from "You Only Live Twice".
If we can pretend they are real (like the jetpack being able to run longer than about 23 seconds, etc.) I'd want Blofeld's mini-sub from "Diamond's Are Forever".
I've always liked that little thing, and wish it had gotten more screen time, like in the original script.
I'd chose the Walther PPK with silencer, it is iconic and potently useful. Those crows that have been attacking, and destroying the windshield wipers, and rubber trim on my Mom's car would find out what .32 acp payback feels like! :lol