(been looking at shoes)
Guinea-Pigs (IMHO)
................but read on.
Everything as stated above, they are lovely, cuddly , friendly, very messy and greedy. What's not to love 
Some are 'gnawing' types -as an adult you wouldn't bat an eyelid. I'd say they'd only ever bite if severely provoked or if your hands smell of food and they mistake your fingers for veg .
At the moment , we have 1yo neutered boar + 2 sows of about 10 months. Recently 'bonded' and happy, but they have loads of space.
Yes you need 2 (+) they aren't happy alone.
Especially if you have boars, they are gorgeous and real people-pigs but if they have any behaviour problems, it usually boils down to dominance and lack of space.
Gumtree gives me the rage
. So many people getting rid because their children have lost interest (Well tell them to Man Up, or as the parent, Man Up Yourself , I reckon) , allergies or getting a dog.
They want a good home. But they also want £25 for an adult second hand guinea-pig (more if you want their shoe-box cage)
If you want guinea-pigs, you are in it for the long-run. When one goes, you need another to keep company.
GP1/GP2 (deceased) GP3/GP4/GP5 are all Rescue. All lovely and snuggly, GP5 has taken a while to settle, but she's sweet and good tempered now.
I did find an Exotics Insurance company for GPs but it was ££.
I paid £58 to have GP3 castrated (general anaesthetic)
Hamsters are (mainly) solitary, you can get hamster palaces to run round, put them in the bath to explore (no water obv) and if you get them from a good rescue or breeder, they'll be handled and sociable.