Pine shavings and rodent waste, basically.
Good garden compost or not? Anything else I can do with this shit besides give it to the trash guy?
Pine shavings will actually co-opt nitrogen from the soil in the process of decomposing. However, you have an awful lot of nitrogen mixed in the shavings in the form of gerbil and guinea pig pee. I’d compost it first rather than putting it directly in the garden. But you could certainly use it rather than sending it to the landfill.
I was actually wondering just last week whether I could put the guinea pig litter out to be collected with the yard waste rather than in the weekly trash pickup. The city composts it all, and there’s nothing inorganic in there, just wood chips and pig pee and poop and whatever hay doesn’t get eaten.
You’ll have to check - many ‘green waste’ composting schemes do permit the inclusion of herbivore wastes, but some don’t permit even that.
Sawdust from animal hutches does compost fairly well - especially if you combine it with grass clippings, or pee on it yourself (after removing it from the hutch, probably)
As a quick aside. . .I had a client/friend insist that there was something found only in dog urine that burns his grass. To prove him wrong, I urinated a time or two every day in my back yard in the same general area (an area I wanted to remove the grass from, coincidentally). My hypothesis was proven!
When I told him the results of my experiment, he said that if he knew I was going to go through all that trouble, he woulda made the original claim regarding dog feces. :eek:
/hijack 
I believe it is actually true that bitch urine is harmful to grass on first application - that is, a single incident will result in a dead patch. I think it’s just too much nitrogen for the plants to be able to cope with.
Not sure, of course, if the same is true of human urine.