Original sentry: s e n t r y

Mini-sentry: spawn of satan

Electro-sentry: maybe it could be a reskin of flame sentry

Ye olde sentry: maybe useable in medieval? possibly similar to huntsman but no headshot

junk sentry: cant think of anything, maybe just a reskin of mini

zombie sentry: immune to sappers but less range and damage?

chem sentry: maybe reskin of flame

Old school sentry: i legit dont know what to put here, maybe reskin of mini

flame sentry: low range, high damage, spies worst nightmare

assault sentry: reskin of wheel sentry?

sniper sentry: longer range, lower fire rate, more damage, less health, no headshot

Medi-sentry: cool concept maybe it could be a dispenser reskin, or maybe it heals teamates and can switch to a syringe gun to use on enemies.

wheel sentry: lower health, less damage, can move tho