1. Something or someone that is funny, energizing, fascinating or exciting.
2. Something or someone that is sexy, alluring, attractive or enticing.
3. Something that is worthy of being snagged.
Use it in when the average word doesn't do it justice:
OMG! When she jumped of the roof into the pool, it was so snaggalicious! or
Wow! That dress is snaggalicious! You look tight!