I kept my spotted with a variety of tankmates, but the constants were a TSN, Clown Knife, Silver Aro, and polyterus sengalus and polypterus palmas. Never any problems, gar actually developed quite a loving relationship with my silver aro.
Kept it with a large pleco and they got along great till the pleco died. Kept it with a small pleco and the little punk harassed my gar. Stay away from pleco's, most other "oddball" or non-aggressive large fish are good for them.