I usually have a SIM pin, but since changing mobile providers, by new SIM card came with no pin, and I haven't set one yet.
Pattern, although I do make my smartwatch and home trusted, and use CM Security App Lock for more private apps.
Sometimes a PIN, other times nothing. I like the idea of the fingerprint scanner, and may just buy another phone to get that feature.
What to Do If You Forget Your Android Phone’s PIN, Pattern, or Password http://www.howtogeek.com/226942/wha...your-android-phone’s-pin-pattern-or-password/
I use a passphrase to secure my android phone. It's a bit inconvenient, but its a requirement after enabling built-in encryption. I've input the passphrase enough that I've got it memorized, but it is reasonably complex. I'm under no illusion that the encryption and passphrase alone are probably not sufficient for securing my device against an attacker with greater resources and knowledge, but at least its not a four digit pin.
Bought a new phone with a fingerprint scanner. Totally worth it. No more effort to use than no security at all. You have to press the power button anyway.