Tinker is a rare class. Cross between beastmaster with strong companion and alchemist with bombs.
Weapon: Automatic crossbow (1d6)
Mechanical companion - a mechanical animal companion. Slower movement. On a 1 it jams and needs repair to function again. Has good armor.
Explosive charge - Delayed blast. Can blow doors and other items open. Gunpowder!
Long range rocket - firecracker like long range explosive rocket. Set and lit as move action.
Bombs - aoe bomb, regular bomb, smoke bomb.
Automatic Crossbow - fire two shots at reduced damage modifier. On 1, the item jams and requires repair with lore: engineering.
Stun gun - shock and stun enemy. Upgrade: arc lightning - zaps an enemy at range and stuns. Move action to crank and make static electricity.
Rocket boots - can fly briefly, or run very fast for one round. Must be repaired to work again.
Upgrade - Make crossbow fire better (no damage reduction and extra shot), or add something to mechanical companion (aquatic mode - no rust, can move underwater, steam engine (adds movement to companion), alarm mode - head spins, makes noise to awaken party, and companion shares full hp of tinker.
Mad bomber - can fuse two bombs together, combining their effect but increasing malfunction chance.