ive had a GT in with parachromis loisellei, gold sev, convict, uaru A., firemouths, filament barbs, a garra (a sto-away from an online order), bristlenose plec, clown loaches and an oscar.
my GT was pretty calm though, a good tank boss. he used to fight with the male BN plec alot but the plec used to start it. i tried a syno cat and the GT went medievil on it after it nipped his fin. it ended up in a mess so i never tried anymore syno cats after that but i others on here have done it without issues.