I had/still have Armory Secure Bitcoin wallet on my lower powered debian mid tower. It was full of features, including cold storage and paper wallet. I set-up a paper wallet. Nice GUI.
But it took a bitch of time to sync with the whole bitcoin blockchain. And occasionally it would lock up, and I would have to restart it. A few of times I had to reset all the databases to refresh and resync, and once I had to reinstall.
Seemed a bit resource hungry, but then again it was a full feature set.
I also have a web BTC wallet with blockchain.info, which for a web wallet seems fairly secure. This in regards to a exchange wallet (like MtGox).
I also have a wallet on my mobile, but consider that quite insecure. So not much kept on the mobile - a coffee and a meal for two.
Of course I have the standard official Linux LTC wallet, downloaded from litecoin.org.