>>9317429For canister sized characters, Tahu Mata is a must, along side a Metru style Toa. I'd also recommend any of the Glatorian/Legends as they really ended up being solid looking figures despite the Inika style builds and crappy sockets. My personal favourites are Malum, Stronius and Strakk. The Barraki are all pretty nifty too.
For small sets, A Turaga is fantastic if only to compare it to everything that came after. They're ridiculously primitive but bursting with personality. McToran are iconic.
For titan sized most are pretty great. Fenrakk, Keetongu, Brutaka, Nocturn, Gadunka, Maxilos, Teridax - all fantastic picks.
Rahi are their own special category. - Bahrag and Muaka/Kane-Ra are defo worth the price tag for just how cool they are as Technic creatures.
Vehicles are hit or miss. My personal favourite is the Jetrax, though Thornatus is pretty cool too.
Honorable mentions for Uniter Onua, Umarak the Hunter, Toa Ekimu and the Toa Masters from G2 for being incredibly solid sets all around.