Do not call with AK or AQ. The only time you're in good shape there is if he is dominated. Most of the time he'll have two live cards and you're only a 60/40 favorite there. I'd call with QQ+, JJ sometimes too. With those hands, there's a BIG chance he has two undercards, an underpair, or just one overcard - so you'll be more than a 70% favorite in all those cases. I'm pretty sure the math says only call with KK/AA though.

Let's say you call with 55 and he has A2 - A5, K2 - K5, Q2- Q5, J2 - J5, T2 - T5, 92 - 95, 82 - 85, 72 - 75, 62 - 65, 52 - 54, 53, 52, 43, 42, 32, 44, 33, 22. You're in great shape against this range. You're in bad shape against 66 - AA. You're in a +EV situation vs any 2 random cards above 55 pretty much, even if it is a coinflip, it's still +EV. Sure, you're not desperate, but this guy is donking off chips and you want them. I'm not passing up a pretty decently +EV opportunity just because i'm scared of busting out, there's always another SNG to join. Sure your variance will increase but so will your ROI in the long run.

I'm with CJ. Leave him alone and take him HU. I'll call with AA - KK but not much else. You can't win from the rail and firing up another SnG is giving up on ths one.