i use a kryptoflex to secure my back wheel to frame and then a kryptonite ny 3000 which i i absolutely love.
probably going to get a mini kryptonite which will take up less space in my bag than the kryptoflex.
invest in good locks! a guy i know had his mtb stolen in leeds city centre and when i asked if he had a good lock he didnt have a clue about whether locks were good or not DICK!
i have good locks but i cant really do anything about the cunt who keeps leaving our bike cellar open at my halls.