Thank you to everyone. This has been helpful. Anyone have any other items not mentioned yet?
I have to say that I have settled on 6 things that are huge for me:
1. 3 Liter Camelbak hydration pack.
2. A telescoping mechanics mirror
3. A telescoping walking stick (I have come to depend on this so much to poke and prod)
4. A nano cache log roller (an incredibly simple little gadget but extremely helpful)
5. Fisher Space Pen - Military model - writes on wet logs
6. Tactical LED flashlight - 200 lumens very small (expensive batteries but worth it)
As far as the thing bought specifically to go after certain caches: 29er mountain bike