I'd also pick dragons or a direwolf (not that they've been particularly useful, eh?) but assuming that the question demands human bodyguards, I'd pick the following (on criteria of fitness for purpose and how annoying they'd be to have around 24/7):
1) Syrio Forel - Great fighter, loyal to the quick. Slightly annoying Braavos speech patterns, but would be worth putting up with for what would be undoubtably top-notch bodyguarding.
2) Howland Reed - I don't really need to say much, eh? Slaying Kingsguard seems to come naturally to this guy (I'm convinced of his eminent Value). Missed out on the top spot by being a little too enigmatic - may have countless bad habits we don't know about.
3) xxxxx - the lovechild of Jaime and Brienne. We all know it's coming, eh? Brienne's brute strength and loyalty and Jaime's speed, skill and calculation. I'm happy taking care of myself for twenty years whilst this one learns the family trade.
okay, okay, I'm not allowed people who haven't been invented yet... jeez... In which case, I'd pick:
3) Ned Stark - Fiercely loyal, good man in a fight. Bit dull though.
Reasons for dismissing the others:
Ser Gregor Clegane - too nuts, too evil
Sandor Clegane - too nuts, too hideously disfigured
Ser Barristan Selmy - too old, too rubbish at keeping the bodies he's supposed to be guarding alive (don't give me excuses, look at the figures)
Strong Belwas - too eccentric, too annoying
Ser Jaime Lannister (pre-injury) - too arrogant, too untrustworthy
Ser Jaime Lannister (post-injury) - too few hands, too unlucky
Brienne of Tarth - too hideously disfigured, too unlucky
Ser Jorah Mormont - too untrustworthy, too boring
Jaqan H'Ghar - too nuts, too evil, way too scary
Khal Drogo - too arrogant
Ser Bronn - too untrustworthy
Oberon Martel - too arrogant, too annoying
Areo Hotah - too forgettable
Ser Arthur Dayne - too shiny
Qhorin Halfhand - too few hands
Jon Snow (Ghost allowed to assist) - too annoying (Ghost almost swings it, but not quite)