I will start:
Shifter Cable nut issue
The H2s and other GMs are know for there shifters to get stuck. This is usually because if you look underneathe the truck the shifter cable has detached itself from the shifter link that is attached to the shifter in the cab.
This happens because the placement of the shifter linkage is so close to a HOT transmission and the "bushing" or "nut" that holds it in is exposed to those temperatures. This causes the plastic bushing to get brittle and over time it breaks.
The fix used to be to buy a whole new cable assembly for about $125 just to get the "bushing" or "nut". Now you can spend about 3 bucks and get it done, probably even better.
Here is a post on another forum about it, including a write up on the fix and pictures
Hope this helps
http://www.hummerforums.com/forum/hu...ing-kit-32747/