I've used nearly every domain registrar out there and here are the ones I'd recommend:

http://www.uniregistrar.com (two-factor, free privacy, cayman islands)

http://www.easydns.com (two-factor, canadian)

http://www.pairnic.com (super lock, requires id to unlock if you enable it)

http://www.dyn.com

http://www.namebright.com (two-factor)

http://www.name.com (two-factor)

http://www.gandi.net (two-factor)

Security is really important for your name so make sure you go with someone who offers some sort of two-factor or extra security lock.