I trust bitcoin-qt most, obviously...
So do I, I guess the more relevant question is, do I trust the computer on which it runs? (NO - scared to type in my password)
Also....
I trust myself more than an online exchange or something. And that's the whole point of bitcoin. Don't put your coins in the hands of a third party. If you are scared of keyloggers:
1. Use an antivirus and don't get keylogged
2. Store your coins in cold storage. Only keep a small amount in your bitcoin-qt client.
Thirdparties are great. We should have bitcoin banks, banks in the TRADITIONAL sense i.e a security service provided by a third party. Bitcoin banks would make a lot of sense for the less tech savvy, they would not become investment banks like we have today, but just provide a service people are going to/already want.