My Sony Ericsson T630 - which I'm STILL getting used to after more than half a year. It's strengthened my conviction that I'm still a Nokie at heart.
Tried switching off my phone for a few minutes after it hanged on me, thinking that 'rebooting' the system will help curb the lagging and hanging.
Only to realise my T9 predictive dictionary, where I have painstakingly built up my vocab in, has been ingeniously reset as well.
Not a very pleasing discovery for a person who types faster than the words appear on the laggy phone.